Traits 3 to Traits 4 view problem with visible_when

[Brennan Williams]

I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.

I'm creating a view for an object (called a vector). It is of class
RZVector.
  It can have an associated vector so I have the RZVector class has a
trait called avector which is defined as an Instance("RZVector").
If the vector doesn't have an associated vector then avector=None

Under Traits 3.x the following was ok...

view=View(
                Item('object.avector.name',visible_when='avector'),
                etc.etc.
)

This is actually in quite a complex view but basically it worked and I  
use visible_when='avector' quite a lot in the view.

In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
i.e. avector is not None

If a vector=None then I get the following error

Traceback (most recent call last):
   File "c:\python27\lib\site-packages\traitsui\wx\tree_editor.py", line
1225, in _on_tree_sel_changed
     kind   = 'subpanel' )
   File "c:\python27\lib\site-packages\traits\has_traits.py", line 2266,
in edit_traits
     handler, id, scrollable, args )
   File "c:\python27\lib\site-packages\traitsui\view.py", line 433, in ui
     ui.ui( parent, kind )
   File "c:\python27\lib\site-packages\traitsui\ui.py", line 218, in ui
     self.rebuild( self, parent )
   File "c:\python27\lib\site-packages\traitsui\wx\toolkit.py", line
126, in ui_subpanel
     ui_panel.ui_subpanel( ui, parent )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
100, in ui_subpanel
     ui_panel_for( ui, parent, False )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
113, in ui_panel_for
     ui.control = control = Panel( ui, parent, buttons ).control
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
202, in __init__
     sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
349, in panel
     content[0], ui )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
523, in fill_panel_for_group
     create_panel )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
670, in __init__
     self.add_groups( content, panel )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
822, in add_groups
     fill_panel_for_group( panel, subgroup, self.ui )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
523, in fill_panel_for_group
     create_panel )
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
672, in __init__
     self.add_items(content, panel, self.sizer)
   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
975, in add_items
     trait  = object.base_trait( name )
AttributeError: 'NoneType' object has no attribute 'base_trait'

One final point. After I create my view, if I print it out there is no
mention of visible_when. It looks like it is ignoring visible_when.

Brennan


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[Jonathan March]

Brennan,

What you are seeing is the expected behavior with ETS 4, but it is also
what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.

Can you extract a simple example which works as you want in ETS 3 but not
in ETS 4?

Jonathan

On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams <
[hidden email]> wrote:

> I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>
> I'm creating a view for an object (called a vector). It is of class
> RZVector.
>  It can have an associated vector so I have the RZVector class has a
> trait called avector which is defined as an Instance("RZVector").
> If the vector doesn't have an associated vector then avector=None
>
> Under Traits 3.x the following was ok...
>
> view=View(
>                Item('object.avector.name',visible_when='avector'),
>                etc.etc.
> )
>
> This is actually in quite a complex view but basically it worked and I
> use visible_when='avector' quite a lot in the view.
>
> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
> i.e. avector is not None
>
> If a vector=None then I get the following error
>
> Traceback (most recent call last):
>   File "c:\python27\lib\site-packages\traitsui\wx\tree_editor.py", line
> 1225, in _on_tree_sel_changed
>     kind   = 'subpanel' )
>   File "c:\python27\lib\site-packages\traits\has_traits.py", line 2266,
> in edit_traits
>     handler, id, scrollable, args )
>   File "c:\python27\lib\site-packages\traitsui\view.py", line 433, in ui
>     ui.ui( parent, kind )
>   File "c:\python27\lib\site-packages\traitsui\ui.py", line 218, in ui
>     self.rebuild( self, parent )
>   File "c:\python27\lib\site-packages\traitsui\wx\toolkit.py", line
> 126, in ui_subpanel
>     ui_panel.ui_subpanel( ui, parent )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 100, in ui_subpanel
>     ui_panel_for( ui, parent, False )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 113, in ui_panel_for
>     ui.control = control = Panel( ui, parent, buttons ).control
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 202, in __init__
>     sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 349, in panel
>     content[0], ui )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 523, in fill_panel_for_group
>     create_panel )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 670, in __init__
>     self.add_groups( content, panel )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 822, in add_groups
>     fill_panel_for_group( panel, subgroup, self.ui )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 523, in fill_panel_for_group
>     create_panel )
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 672, in __init__
>     self.add_items(content, panel, self.sizer)
>   File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
> 975, in add_items
>     trait  = object.base_trait( name )
> AttributeError: 'NoneType' object has no attribute 'base_trait'
>
> One final point. After I create my view, if I print it out there is no
> mention of visible_when. It looks like it is ignoring visible_when.
>
> Brennan
>
>
> _______________________________________________
> Enthought-Dev mailing list
> [hidden email]
> https://mail.enthought.com/mailman/listinfo/enthought-dev
>

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[Brennan Williams]

On 14/02/2012 6:54 a.m., Jonathan March wrote:
> Brennan,
>
> What you are seeing is the expected behavior with ETS 4, but it is also
> what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.
>
> Can you extract a simple example which works as you want in ETS 3 but not
> in ETS 4?
See attached. I've left the imports as enthought. so it runs under both
EPD 6.2 and 7.2 but in my own code I've switched to the new format.

Brennan

> Jonathan
>
> On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams<
> [hidden email]>  wrote:
>
>> I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>>
>> I'm creating a view for an object (called a vector). It is of class
>> RZVector.
>>   It can have an associated vector so I have the RZVector class has a
>> trait called avector which is defined as an Instance("RZVector").
>> If the vector doesn't have an associated vector then avector=None
>>
>> Under Traits 3.x the following was ok...
>>
>> view=View(
>>                 Item('object.avector.name',visible_when='avector'),
>>                 etc.etc.
>> )
>>
>> This is actually in quite a complex view but basically it worked and I
>> use visible_when='avector' quite a lot in the view.
>>
>> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
>> i.e. avector is not None
>>
>> If a vector=None then I get the following error
>>
>> Traceback (most recent call last):
>>    File "c:\python27\lib\site-packages\traitsui\wx\tree_editor.py", line
>> 1225, in _on_tree_sel_changed
>>      kind   = 'subpanel' )
>>    File "c:\python27\lib\site-packages\traits\has_traits.py", line 2266,
>> in edit_traits
>>      handler, id, scrollable, args )
>>    File "c:\python27\lib\site-packages\traitsui\view.py", line 433, in ui
>>      ui.ui( parent, kind )
>>    File "c:\python27\lib\site-packages\traitsui\ui.py", line 218, in ui
>>      self.rebuild( self, parent )
>>    File "c:\python27\lib\site-packages\traitsui\wx\toolkit.py", line
>> 126, in ui_subpanel
>>      ui_panel.ui_subpanel( ui, parent )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 100, in ui_subpanel
>>      ui_panel_for( ui, parent, False )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 113, in ui_panel_for
>>      ui.control = control = Panel( ui, parent, buttons ).control
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 202, in __init__
>>      sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 349, in panel
>>      content[0], ui )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 523, in fill_panel_for_group
>>      create_panel )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 670, in __init__
>>      self.add_groups( content, panel )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 822, in add_groups
>>      fill_panel_for_group( panel, subgroup, self.ui )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 523, in fill_panel_for_group
>>      create_panel )
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 672, in __init__
>>      self.add_items(content, panel, self.sizer)
>>    File "c:\python27\lib\site-packages\traitsui\wx\ui_panel.py", line
>> 975, in add_items
>>      trait  = object.base_trait( name )
>> AttributeError: 'NoneType' object has no attribute 'base_trait'
>>
>> One final point. After I create my view, if I print it out there is no
>> mention of visible_when. It looks like it is ignoring visible_when.
>>
>> Brennan
>>
>>
>> _______________________________________________
>> Enthought-Dev mailing list
>> [hidden email]
>> https://mail.enthought.com/mailman/listinfo/enthought-dev
>>
> _______________________________________________
> Enthought-Dev mailing list
> [hidden email]
> https://mail.enthought.com/mailman/listinfo/enthought-dev
>

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[Simon Jagoe]

I don't know if this is the cause of the problem (I don't have ETS on the
computer I am currently on), but you will have undefined behaviour if you
do not call "super(Person, self).__init__()".

Also, I would suggest removing the __init__ completely and passing input
values as keyword arguments and letting Traits do the initialization.

On Mon, Feb 13, 2012 at 9:15 PM, Brennan Williams <
[hidden email]> wrote:

> On 14/02/2012 6:54 a.m., Jonathan March wrote:
>
>> Brennan,
>>
>> What you are seeing is the expected behavior with ETS 4, but it is also
>> what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.
>>
>> Can you extract a simple example which works as you want in ETS 3 but not
>> in ETS 4?
>>
> See attached. I've left the imports as enthought. so it runs under both
> EPD 6.2 and 7.2 but in my own code I've switched to the new format.
>
> Brennan
>
>  Jonathan
>>
>> On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams<
>> brennan.williams@**visualreservoir.com<[hidden email]>>
>>  wrote:
>>
>>  I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>>>
>>> I'm creating a view for an object (called a vector). It is of class
>>> RZVector.
>>>  It can have an associated vector so I have the RZVector class has a
>>> trait called avector which is defined as an Instance("RZVector").
>>> If the vector doesn't have an associated vector then avector=None
>>>
>>> Under Traits 3.x the following was ok...
>>>
>>> view=View(
>>>                Item('object.avector.name',**visible_when='avector'),
>>>                etc.etc.
>>> )
>>>
>>> This is actually in quite a complex view but basically it worked and I
>>> use visible_when='avector' quite a lot in the view.
>>>
>>> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
>>> i.e. avector is not None
>>>
>>> If a vector=None then I get the following error
>>>
>>> Traceback (most recent call last):
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\tree_**editor.py",
>>> line
>>> 1225, in _on_tree_sel_changed
>>>     kind   = 'subpanel' )
>>>   File "c:\python27\lib\site-**packages\traits\has_traits.py"**, line
>>> 2266,
>>> in edit_traits
>>>     handler, id, scrollable, args )
>>>   File "c:\python27\lib\site-**packages\traitsui\view.py", line 433, in
>>> ui
>>>     ui.ui( parent, kind )
>>>   File "c:\python27\lib\site-**packages\traitsui\ui.py", line 218, in ui
>>>     self.rebuild( self, parent )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\toolkit.**py", line
>>> 126, in ui_subpanel
>>>     ui_panel.ui_subpanel( ui, parent )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 100, in ui_subpanel
>>>     ui_panel_for( ui, parent, False )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 113, in ui_panel_for
>>>     ui.control = control = Panel( ui, parent, buttons ).control
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 202, in __init__
>>>     sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 349, in panel
>>>     content[0], ui )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 523, in fill_panel_for_group
>>>     create_panel )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 670, in __init__
>>>     self.add_groups( content, panel )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 822, in add_groups
>>>     fill_panel_for_group( panel, subgroup, self.ui )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 523, in fill_panel_for_group
>>>     create_panel )
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 672, in __init__
>>>     self.add_items(content, panel, self.sizer)
>>>   File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>> 975, in add_items
>>>     trait  = object.base_trait( name )
>>> AttributeError: 'NoneType' object has no attribute 'base_trait'
>>>
>>> One final point. After I create my view, if I print it out there is no
>>> mention of visible_when. It looks like it is ignoring visible_when.
>>>
>>> Brennan
>>>
>>>
>>> ______________________________**_________________
>>> Enthought-Dev mailing list
>>> [hidden email].**com <[hidden email]>
>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>
>>>  ______________________________**_________________
>> Enthought-Dev mailing list
>> [hidden email].**com <[hidden email]>
>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>
>>
>
> _______________________________________________
> Enthought-Dev mailing list
> [hidden email]
> https://mail.enthought.com/mailman/listinfo/enthought-dev
>
>

--
Simon Jagoe
Enthought Ltd
[phone]
[hidden email]
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[Brennan Williams]

On 14/02/2012 10:22 a.m., Simon Jagoe wrote:
> I don't know if this is the cause of the problem (I don't have ETS on the
> computer I am currently on), but you will have undefined behaviour if you
> do not call "super(Person, self).__init__()".
ok I'll look into that
> Also, I would suggest removing the __init__ completely and passing input
> values as keyword arguments and letting Traits do the initialization.
Sorry, can you clarify what you mean by that?

>
> On Mon, Feb 13, 2012 at 9:15 PM, Brennan Williams<
> [hidden email]>  wrote:
>
>> On 14/02/2012 6:54 a.m., Jonathan March wrote:
>>
>>> Brennan,
>>>
>>> What you are seeing is the expected behavior with ETS 4, but it is also
>>> what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.
>>>
>>> Can you extract a simple example which works as you want in ETS 3 but not
>>> in ETS 4?
>>>
>> See attached. I've left the imports as enthought. so it runs under both
>> EPD 6.2 and 7.2 but in my own code I've switched to the new format.
>>
>> Brennan
>>
>>   Jonathan
>>> On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams<
>>> brennan.williams@**visualreservoir.com<[hidden email]>>
>>>   wrote:
>>>
>>>   I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>>>> I'm creating a view for an object (called a vector). It is of class
>>>> RZVector.
>>>>   It can have an associated vector so I have the RZVector class has a
>>>> trait called avector which is defined as an Instance("RZVector").
>>>> If the vector doesn't have an associated vector then avector=None
>>>>
>>>> Under Traits 3.x the following was ok...
>>>>
>>>> view=View(
>>>>                 Item('object.avector.name',**visible_when='avector'),
>>>>                 etc.etc.
>>>> )
>>>>
>>>> This is actually in quite a complex view but basically it worked and I
>>>> use visible_when='avector' quite a lot in the view.
>>>>
>>>> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
>>>> i.e. avector is not None
>>>>
>>>> If a vector=None then I get the following error
>>>>
>>>> Traceback (most recent call last):
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\tree_**editor.py",
>>>> line
>>>> 1225, in _on_tree_sel_changed
>>>>      kind   = 'subpanel' )
>>>>    File "c:\python27\lib\site-**packages\traits\has_traits.py"**, line
>>>> 2266,
>>>> in edit_traits
>>>>      handler, id, scrollable, args )
>>>>    File "c:\python27\lib\site-**packages\traitsui\view.py", line 433, in
>>>> ui
>>>>      ui.ui( parent, kind )
>>>>    File "c:\python27\lib\site-**packages\traitsui\ui.py", line 218, in ui
>>>>      self.rebuild( self, parent )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\toolkit.**py", line
>>>> 126, in ui_subpanel
>>>>      ui_panel.ui_subpanel( ui, parent )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 100, in ui_subpanel
>>>>      ui_panel_for( ui, parent, False )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 113, in ui_panel_for
>>>>      ui.control = control = Panel( ui, parent, buttons ).control
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 202, in __init__
>>>>      sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 349, in panel
>>>>      content[0], ui )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 523, in fill_panel_for_group
>>>>      create_panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 670, in __init__
>>>>      self.add_groups( content, panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 822, in add_groups
>>>>      fill_panel_for_group( panel, subgroup, self.ui )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 523, in fill_panel_for_group
>>>>      create_panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 672, in __init__
>>>>      self.add_items(content, panel, self.sizer)
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 975, in add_items
>>>>      trait  = object.base_trait( name )
>>>> AttributeError: 'NoneType' object has no attribute 'base_trait'
>>>>
>>>> One final point. After I create my view, if I print it out there is no
>>>> mention of visible_when. It looks like it is ignoring visible_when.
>>>>
>>>> Brennan
>>>>
>>>>
>>>> ______________________________**_________________
>>>> Enthought-Dev mailing list
>>>> [hidden email].**com<[hidden email]>
>>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>>
>>>>   ______________________________**_________________
>>> Enthought-Dev mailing list
>>> [hidden email].**com<[hidden email]>
>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>
>>>
>> _______________________________________________
>> Enthought-Dev mailing list
>> [hidden email]
>> https://mail.enthought.com/mailman/listinfo/enthought-dev
>>
>>
>

_______________________________________________
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[Brennan Williams]

On 14/02/2012 10:22 a.m., Simon Jagoe wrote:
> I don't know if this is the cause of the problem (I don't have ETS on the
> computer I am currently on), but you will have undefined behaviour if you
> do not call "super(Person, self).__init__()".
No change when I added super. Still working ok under EPD 6.2 and the
'NoneType' object has no attribute 'base_trait' error under EPD 7.2.
I looked at the traitsui\wx\ui_panel.py code for both and I couldn't see
why they work differently.

Have I just been getting away with this under previous versions?

>
> Also, I would suggest removing the __init__ completely and passing input
> values as keyword arguments and letting Traits do the initialization.
>
> On Mon, Feb 13, 2012 at 9:15 PM, Brennan Williams<
> [hidden email]>  wrote:
>
>> On 14/02/2012 6:54 a.m., Jonathan March wrote:
>>
>>> Brennan,
>>>
>>> What you are seeing is the expected behavior with ETS 4, but it is also
>>> what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.
>>>
>>> Can you extract a simple example which works as you want in ETS 3 but not
>>> in ETS 4?
>>>
>> See attached. I've left the imports as enthought. so it runs under both
>> EPD 6.2 and 7.2 but in my own code I've switched to the new format.
>>
>> Brennan
>>
>>   Jonathan
>>> On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams<
>>> brennan.williams@**visualreservoir.com<[hidden email]>>
>>>   wrote:
>>>
>>>   I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>>>> I'm creating a view for an object (called a vector). It is of class
>>>> RZVector.
>>>>   It can have an associated vector so I have the RZVector class has a
>>>> trait called avector which is defined as an Instance("RZVector").
>>>> If the vector doesn't have an associated vector then avector=None
>>>>
>>>> Under Traits 3.x the following was ok...
>>>>
>>>> view=View(
>>>>                 Item('object.avector.name',**visible_when='avector'),
>>>>                 etc.etc.
>>>> )
>>>>
>>>> This is actually in quite a complex view but basically it worked and I
>>>> use visible_when='avector' quite a lot in the view.
>>>>
>>>> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
>>>> i.e. avector is not None
>>>>
>>>> If a vector=None then I get the following error
>>>>
>>>> Traceback (most recent call last):
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\tree_**editor.py",
>>>> line
>>>> 1225, in _on_tree_sel_changed
>>>>      kind   = 'subpanel' )
>>>>    File "c:\python27\lib\site-**packages\traits\has_traits.py"**, line
>>>> 2266,
>>>> in edit_traits
>>>>      handler, id, scrollable, args )
>>>>    File "c:\python27\lib\site-**packages\traitsui\view.py", line 433, in
>>>> ui
>>>>      ui.ui( parent, kind )
>>>>    File "c:\python27\lib\site-**packages\traitsui\ui.py", line 218, in ui
>>>>      self.rebuild( self, parent )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\toolkit.**py", line
>>>> 126, in ui_subpanel
>>>>      ui_panel.ui_subpanel( ui, parent )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 100, in ui_subpanel
>>>>      ui_panel_for( ui, parent, False )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 113, in ui_panel_for
>>>>      ui.control = control = Panel( ui, parent, buttons ).control
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 202, in __init__
>>>>      sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 349, in panel
>>>>      content[0], ui )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 523, in fill_panel_for_group
>>>>      create_panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 670, in __init__
>>>>      self.add_groups( content, panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 822, in add_groups
>>>>      fill_panel_for_group( panel, subgroup, self.ui )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 523, in fill_panel_for_group
>>>>      create_panel )
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 672, in __init__
>>>>      self.add_items(content, panel, self.sizer)
>>>>    File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>> 975, in add_items
>>>>      trait  = object.base_trait( name )
>>>> AttributeError: 'NoneType' object has no attribute 'base_trait'
>>>>
>>>> One final point. After I create my view, if I print it out there is no
>>>> mention of visible_when. It looks like it is ignoring visible_when.
>>>>
>>>> Brennan
>>>>
>>>>
>>>> ______________________________**_________________
>>>> Enthought-Dev mailing list
>>>> [hidden email].**com<[hidden email]>
>>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>>
>>>>   ______________________________**_________________
>>> Enthought-Dev mailing list
>>> [hidden email].**com<[hidden email]>
>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>
>>>
>> _______________________________________________
>> Enthought-Dev mailing list
>> [hidden email]
>> https://mail.enthought.com/mailman/listinfo/enthought-dev
>>
>>
>

_______________________________________________
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[Brennan Williams]

On 14/02/2012 10:33 a.m., Brennan Williams wrote:
> On 14/02/2012 10:22 a.m., Simon Jagoe wrote:
>> I don't know if this is the cause of the problem (I don't have ETS on the
>> computer I am currently on), but you will have undefined behaviour if you
>> do not call "super(Person, self).__init__()".
> ok I'll look into that
>> Also, I would suggest removing the __init__ completely and passing input
>> values as keyword arguments and letting Traits do the initialization.
> Sorry, can you clarify what you mean by that?
DId you mean...

from enthought.traits.api import HasTraits, Str, Instance
from enthought.traits.ui.api import View, Item, VGroup
from enthought.traits.ui.api import Handler
from enthought.pyface.api import error, information, warning

class Person(HasTraits):
     first_name = Str("Joe")
     last_name = Str("Blow")
     partner=Instance("Person")

     view = View('first_name', 'last_name',
          VGroup(
           
Item('object.partner.first_name',style='readonly',visible_when='partner'),
           
Item('object.partner.last_name',style='readonly',visible_when='partner'),
            label='Partner',
          ),
        )

#    def __init__(self,first,last,partner):
#    super(Person,self).__init__()
#        self.first_name=first
#    self.last_name=last
#    if partner:
#        self.partner=partner



gill = Person(first_name='Gill',last_name='Jones',partner=None)
sam = Person(first_name='Sam',last_name='Smith',partner=gill)
sam.configure_traits()
gill.configure_traits()


That still has the same behaviour - works in EPD 6.2, doesn't in 7.2 by
which I suppose I really mean Traits 3 vs Traits 4.

>> On Mon, Feb 13, 2012 at 9:15 PM, Brennan Williams<
>> [hidden email]>   wrote:
>>
>>> On 14/02/2012 6:54 a.m., Jonathan March wrote:
>>>
>>>> Brennan,
>>>>
>>>> What you are seeing is the expected behavior with ETS 4, but it is also
>>>> what I see in a simple example with EPD 6.2 (ETS 3), at least on OSX.
>>>>
>>>> Can you extract a simple example which works as you want in ETS 3 but not
>>>> in ETS 4?
>>>>
>>> See attached. I've left the imports as enthought. so it runs under both
>>> EPD 6.2 and 7.2 but in my own code I've switched to the new format.
>>>
>>> Brennan
>>>
>>>    Jonathan
>>>> On Mon, Feb 13, 2012 at 3:56 AM, Brennan Williams<
>>>> brennan.williams@**visualreservoir.com<[hidden email]>>
>>>>    wrote:
>>>>
>>>>    I'm moving from EPD 6.2 to 7.2 on a 32-bit Windows 7 platform using wx.
>>>>> I'm creating a view for an object (called a vector). It is of class
>>>>> RZVector.
>>>>>    It can have an associated vector so I have the RZVector class has a
>>>>> trait called avector which is defined as an Instance("RZVector").
>>>>> If the vector doesn't have an associated vector then avector=None
>>>>>
>>>>> Under Traits 3.x the following was ok...
>>>>>
>>>>> view=View(
>>>>>                  Item('object.avector.name',**visible_when='avector'),
>>>>>                  etc.etc.
>>>>> )
>>>>>
>>>>> This is actually in quite a complex view but basically it worked and I
>>>>> use visible_when='avector' quite a lot in the view.
>>>>>
>>>>> In Traits 4 (epd 7.2.2) the view is ok if there is an associated vector,
>>>>> i.e. avector is not None
>>>>>
>>>>> If a vector=None then I get the following error
>>>>>
>>>>> Traceback (most recent call last):
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\tree_**editor.py",
>>>>> line
>>>>> 1225, in _on_tree_sel_changed
>>>>>       kind   = 'subpanel' )
>>>>>     File "c:\python27\lib\site-**packages\traits\has_traits.py"**, line
>>>>> 2266,
>>>>> in edit_traits
>>>>>       handler, id, scrollable, args )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\view.py", line 433, in
>>>>> ui
>>>>>       ui.ui( parent, kind )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\ui.py", line 218, in ui
>>>>>       self.rebuild( self, parent )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\toolkit.**py", line
>>>>> 126, in ui_subpanel
>>>>>       ui_panel.ui_subpanel( ui, parent )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 100, in ui_subpanel
>>>>>       ui_panel_for( ui, parent, False )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 113, in ui_panel_for
>>>>>       ui.control = control = Panel( ui, parent, buttons ).control
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 202, in __init__
>>>>>       sizer.Add( panel( ui, sw ), 1, wx.EXPAND )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 349, in panel
>>>>>       content[0], ui )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 523, in fill_panel_for_group
>>>>>       create_panel )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 670, in __init__
>>>>>       self.add_groups( content, panel )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 822, in add_groups
>>>>>       fill_panel_for_group( panel, subgroup, self.ui )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 523, in fill_panel_for_group
>>>>>       create_panel )
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 672, in __init__
>>>>>       self.add_items(content, panel, self.sizer)
>>>>>     File "c:\python27\lib\site-**packages\traitsui\wx\ui_panel.**py", line
>>>>> 975, in add_items
>>>>>       trait  = object.base_trait( name )
>>>>> AttributeError: 'NoneType' object has no attribute 'base_trait'
>>>>>
>>>>> One final point. After I create my view, if I print it out there is no
>>>>> mention of visible_when. It looks like it is ignoring visible_when.
>>>>>
>>>>> Brennan
>>>>>
>>>>>
>>>>> ______________________________**_________________
>>>>> Enthought-Dev mailing list
>>>>> [hidden email].**com<[hidden email]>
>>>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>>>
>>>>>    ______________________________**_________________
>>>> Enthought-Dev mailing list
>>>> [hidden email].**com<[hidden email]>
>>>> https://mail.enthought.com/**mailman/listinfo/enthought-dev<https://mail.enthought.com/mailman/listinfo/enthought-dev>
>>>>
>>>>
>>> _______________________________________________
>>> Enthought-Dev mailing list
>>> [hidden email]
>>> https://mail.enthought.com/mailman/listinfo/enthought-dev
>>>
>>>
> _______________________________________________
> Enthought-Dev mailing list
> [hidden email]
> https://mail.enthought.com/mailman/listinfo/enthought-dev
>

_______________________________________________
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[Simon Jagoe]

Yes, that is what I meant. I'm afraid I didn't expect it to change
behaviour much, but it is the preferred way of created HasTraits subclasses.

In terms of your problem,

possibly a workaround like this would be acceptable:

class Person(HasTraits):
    first_name = Str("Joe")
    last_name = Str("Blow")
    partner=Instance("Person", args=())
    _display_partner = Bool(False)

    def __init__(self, **traits):
        super(Person, self).__init__(**traits)
        if 'partner' in traits:



DId you mean...

>
> from enthought.traits.api import HasTraits, Str, Instance
> from enthought.traits.ui.api import View, Item, VGroup
> from enthought.traits.ui.api import Handler
> from enthought.pyface.api import error, information, warning
>
> class Person(HasTraits):
>     first_name = Str("Joe")
>     last_name = Str("Blow")
>     partner=Instance("Person")
>
>     view = View('first_name', 'last_name',
>          VGroup(
>
> Item('object.partner.first_name',style='readonly',visible_when='partner'),
>
> Item('object.partner.last_name',style='readonly',visible_when='partner'),
>            label='Partner',
>          ),
>        )
>
> #    def __init__(self,first,last,partner):
> #    super(Person,self).__init__()
> #        self.first_name=first
> #    self.last_name=last
> #    if partner:
> #        self.partner=partner
>
>
>
> gill = Person(first_name='Gill',last_name='Jones',partner=None)
> sam = Person(first_name='Sam',last_name='Smith',partner=gill)
> sam.configure_traits()
> gill.configure_traits()
>
>
>

--
Simon Jagoe
Enthought Ltd
[phone]
[hidden email]
_______________________________________________
Enthought-Dev mailing list
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[Simon Jagoe]

Sorry, accidentally hit send too soon

class Person(HasTraits):
    first_name = Str("Joe")
    last_name = Str("Blow")
    partner=Instance("Person", args=())
    _display_partner = Bool(False)

    def __init__(self, **traits):
        super(Person, self).__init__(**traits)
        if 'partner' in traits:
            self._display_partner = True


then use _display_partner in your visible_when clause.

On Mon, Feb 13, 2012 at 9:57 PM, Simon Jagoe <[hidden email]> wrote:

> Yes, that is what I meant. I'm afraid I didn't expect it to change
> behaviour much, but it is the preferred way of created HasTraits subclasses.
>
> In terms of your problem,
>
> possibly a workaround like this would be acceptable:
>
> class Person(HasTraits):
>     first_name = Str("Joe")
>     last_name = Str("Blow")
>     partner=Instance("Person", args=())
>     _display_partner = Bool(False)
>
>     def __init__(self, **traits):
>         super(Person, self).__init__(**traits)
>         if 'partner' in traits:
>
>
>
> DId you mean...
>>
>> from enthought.traits.api import HasTraits, Str, Instance
>> from enthought.traits.ui.api import View, Item, VGroup
>> from enthought.traits.ui.api import Handler
>> from enthought.pyface.api import error, information, warning
>>
>> class Person(HasTraits):
>>     first_name = Str("Joe")
>>     last_name = Str("Blow")
>>     partner=Instance("Person")
>>
>>     view = View('first_name', 'last_name',
>>          VGroup(
>>
>> Item('object.partner.first_name',style='readonly',visible_when='partner'),
>>
>> Item('object.partner.last_name',style='readonly',visible_when='partner'),
>>            label='Partner',
>>          ),
>>        )
>>
>> #    def __init__(self,first,last,partner):
>> #    super(Person,self).__init__()
>> #        self.first_name=first
>> #    self.last_name=last
>> #    if partner:
>> #        self.partner=partner
>>
>>
>>
>> gill = Person(first_name='Gill',last_name='Jones',partner=None)
>> sam = Person(first_name='Sam',last_name='Smith',partner=gill)
>> sam.configure_traits()
>> gill.configure_traits()
>>
>>
>>
> --
> Simon Jagoe
> Enthought Ltd
> [phone]
> [hidden email]
>

--
Simon Jagoe
Enthought Ltd
[phone]
[hidden email]
_______________________________________________
Enthought-Dev mailing list
[hidden email]
https://mail.enthought.com/mailman/listinfo/enthought-dev

[John Wiggins]

I believe using visible_when="partner is not None" would also work.

- John

On Mon, Feb 13, 2012 at 3:58 PM, Simon Jagoe <[hidden email]> wrote:

> Sorry, accidentally hit send too soon
>
> class Person(HasTraits):
>    first_name = Str("Joe")
>    last_name = Str("Blow")
>    partner=Instance("Person", args=())
>    _display_partner = Bool(False)
>
>    def __init__(self, **traits):
>        super(Person, self).__init__(**traits)
>        if 'partner' in traits:
>            self._display_partner = True
>
>
> then use _display_partner in your visible_when clause.
>
> On Mon, Feb 13, 2012 at 9:57 PM, Simon Jagoe <[hidden email]> wrote:
>
>> Yes, that is what I meant. I'm afraid I didn't expect it to change
>> behaviour much, but it is the preferred way of created HasTraits subclasses.
>>
>> In terms of your problem,
>>
>> possibly a workaround like this would be acceptable:
>>
>> class Person(HasTraits):
>>     first_name = Str("Joe")
>>     last_name = Str("Blow")
>>     partner=Instance("Person", args=())
>>     _display_partner = Bool(False)
>>
>>     def __init__(self, **traits):
>>         super(Person, self).__init__(**traits)
>>         if 'partner' in traits:
>>
>>
>>
>> DId you mean...
>>>
>>> from enthought.traits.api import HasTraits, Str, Instance
>>> from enthought.traits.ui.api import View, Item, VGroup
>>> from enthought.traits.ui.api import Handler
>>> from enthought.pyface.api import error, information, warning
>>>
>>> class Person(HasTraits):
>>>     first_name = Str("Joe")
>>>     last_name = Str("Blow")
>>>     partner=Instance("Person")
>>>
>>>     view = View('first_name', 'last_name',
>>>          VGroup(
>>>
>>> Item('object.partner.first_name',style='readonly',visible_when='partner'),
>>>
>>> Item('object.partner.last_name',style='readonly',visible_when='partner'),
>>>            label='Partner',
>>>          ),
>>>        )
>>>
>>> #    def __init__(self,first,last,partner):
>>> #    super(Person,self).__init__()
>>> #        self.first_name=first
>>> #    self.last_name=last
>>> #    if partner:
>>> #        self.partner=partner
>>>
>>>
>>>
>>> gill = Person(first_name='Gill',last_name='Jones',partner=None)
>>> sam = Person(first_name='Sam',last_name='Smith',partner=gill)
>>> sam.configure_traits()
>>> gill.configure_traits()
>>>
>>>
>>>
>> --
>> Simon Jagoe
>> Enthought Ltd
>> [phone]
>> [hidden email]
>>
>
>
>
> --
> Simon Jagoe
> Enthought Ltd
> [phone]
> [hidden email]
> _______________________________________________
> Enthought-Dev mailing list
> [hidden email]
> https://mail.enthought.com/mailman/listinfo/enthought-dev

_______________________________________________
Enthought-Dev mailing list
[hidden email]
https://mail.enthought.com/mailman/listinfo/enthought-dev

[Brennan Williams]

On 14/02/2012 10:58 a.m., Simon Jagoe wrote:

> Sorry, accidentally hit send too soon
>
> class Person(HasTraits):
>      first_name = Str("Joe")
>      last_name = Str("Blow")
>      partner=Instance("Person", args=())
>      _display_partner = Bool(False)
>
>      def __init__(self, **traits):
>          super(Person, self).__init__(**traits)
>          if 'partner' in traits:
>              self._display_partner = True
>
>
> then use _display_partner in your visible_when clause.

Tried that and it worked. However that means I have a lot of editing to
do in my code.

And I have a confession to make. I should have done this earlier but I
just did a diff on the ui_panel.py in EPD 7.2 with that in EPD 6.2 and
I've realised that I added two lines to it - I did this about 16 months
ago and didn't document it....

but if you look at ui_panel.py aorund line 974 it looks like....

             # Otherwise, it must be a trait Item:
             object = eval( item.object_, globals(), ui.context )
             trait  = object.base_trait( name )
             desc   = trait.desc or ''
             label  = None

and I modified it to...

             # Otherwise, it must be a trait Item:
             object = eval( item.object_, globals(), ui.context )
             if not object:
                  return
             trait  = object.base_trait( name )
             desc   = trait.desc or ''
             label  = None

In my defence I don't remember doing this but it worked.  The processing
of the item name is done before checking whether it is visible or not.

Brennan

>
> On Mon, Feb 13, 2012 at 9:57 PM, Simon Jagoe<[hidden email]>  wrote:
>
>> Yes, that is what I meant. I'm afraid I didn't expect it to change
>> behaviour much, but it is the preferred way of created HasTraits subclasses.
>>
>> In terms of your problem,
>>
>> possibly a workaround like this would be acceptable:
>>
>> class Person(HasTraits):
>>      first_name = Str("Joe")
>>      last_name = Str("Blow")
>>      partner=Instance("Person", args=())
>>      _display_partner = Bool(False)
>>
>>      def __init__(self, **traits):
>>          super(Person, self).__init__(**traits)
>>          if 'partner' in traits:
>>
>>
>>
>> DId you mean...
>>> from enthought.traits.api import HasTraits, Str, Instance
>>> from enthought.traits.ui.api import View, Item, VGroup
>>> from enthought.traits.ui.api import Handler
>>> from enthought.pyface.api import error, information, warning
>>>
>>> class Person(HasTraits):
>>>      first_name = Str("Joe")
>>>      last_name = Str("Blow")
>>>      partner=Instance("Person")
>>>
>>>      view = View('first_name', 'last_name',
>>>           VGroup(
>>>
>>> Item('object.partner.first_name',style='readonly',visible_when='partner'),
>>>
>>> Item('object.partner.last_name',style='readonly',visible_when='partner'),
>>>             label='Partner',
>>>           ),
>>>         )
>>>
>>> #    def __init__(self,first,last,partner):
>>> #    super(Person,self).__init__()
>>> #        self.first_name=first
>>> #    self.last_name=last
>>> #    if partner:
>>> #        self.partner=partner
>>>
>>>
>>>
>>> gill = Person(first_name='Gill',last_name='Jones',partner=None)
>>> sam = Person(first_name='Sam',last_name='Smith',partner=gill)
>>> sam.configure_traits()
>>> gill.configure_traits()
>>>
>>>
>>>
>> --
>> Simon Jagoe
>> Enthought Ltd
>> [phone]
>> [hidden email]
>>
>
>

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[Brennan Williams]

Just thinking about this a bit more.... what I am aiming for is to have
one view definition (which is my app is quite large and includes plots,
array tables etc) whether an instance of class Person has a partner or
not. The reason I'm using visible_when is that you can add a partner
after a person has been created and viewed.

I also have a parent class, e.g. a class Family which has a list of
persons and a family view which uses a TableEditor with a
selected='currentperson' so that you have a combined view of the list
with a current person view underneath.

So my previous mod of adding " if not object: return" to ui_panel.py
worked quite well.

What do you think is the best way for me to handle this?

Brennan

On 14/02/2012 11:59 a.m., Brennan Williams wrote:

> On 14/02/2012 10:58 a.m., Simon Jagoe wrote:
>> Sorry, accidentally hit send too soon
>>
>> class Person(HasTraits):
>>       first_name = Str("Joe")
>>       last_name = Str("Blow")
>>       partner=Instance("Person", args=())
>>       _display_partner = Bool(False)
>>
>>       def __init__(self, **traits):
>>           super(Person, self).__init__(**traits)
>>           if 'partner' in traits:
>>               self._display_partner = True
>>
>>
>> then use _display_partner in your visible_when clause.
> Tried that and it worked. However that means I have a lot of editing to
> do in my code.
>
> And I have a confession to make. I should have done this earlier but I
> just did a diff on the ui_panel.py in EPD 7.2 with that in EPD 6.2 and
> I've realised that I added two lines to it - I did this about 16 months
> ago and didn't document it....
>
> but if you look at ui_panel.py aorund line 974 it looks like....
>
>               # Otherwise, it must be a trait Item:
>               object = eval( item.object_, globals(), ui.context )
>               trait  = object.base_trait( name )
>               desc   = trait.desc or ''
>               label  = None
>
> and I modified it to...
>
>               # Otherwise, it must be a trait Item:
>               object = eval( item.object_, globals(), ui.context )
>               if not object:
>                    return
>               trait  = object.base_trait( name )
>               desc   = trait.desc or ''
>               label  = None
>
> In my defence I don't remember doing this but it worked.  The processing
> of the item name is done before checking whether it is visible or not.
>
> Brennan
>
>> On Mon, Feb 13, 2012 at 9:57 PM, Simon Jagoe<[hidden email]>   wrote:
>>
>>> Yes, that is what I meant. I'm afraid I didn't expect it to change
>>> behaviour much, but it is the preferred way of created HasTraits subclasses.
>>>
>>> In terms of your problem,
>>>
>>> possibly a workaround like this would be acceptable:
>>>
>>> class Person(HasTraits):
>>>       first_name = Str("Joe")
>>>       last_name = Str("Blow")
>>>       partner=Instance("Person", args=())
>>>       _display_partner = Bool(False)
>>>
>>>       def __init__(self, **traits):
>>>           super(Person, self).__init__(**traits)
>>>           if 'partner' in traits:
>>>
>>>
>>>
>>> DId you mean...
>>>> from enthought.traits.api import HasTraits, Str, Instance
>>>> from enthought.traits.ui.api import View, Item, VGroup
>>>> from enthought.traits.ui.api import Handler
>>>> from enthought.pyface.api import error, information, warning
>>>>
>>>> class Person(HasTraits):
>>>>       first_name = Str("Joe")
>>>>       last_name = Str("Blow")
>>>>       partner=Instance("Person")
>>>>
>>>>       view = View('first_name', 'last_name',
>>>>            VGroup(
>>>>
>>>> Item('object.partner.first_name',style='readonly',visible_when='partner'),
>>>>
>>>> Item('object.partner.last_name',style='readonly',visible_when='partner'),
>>>>              label='Partner',
>>>>            ),
>>>>          )
>>>>
>>>> #    def __init__(self,first,last,partner):
>>>> #    super(Person,self).__init__()
>>>> #        self.first_name=first
>>>> #    self.last_name=last
>>>> #    if partner:
>>>> #        self.partner=partner
>>>>
>>>>
>>>>
>>>> gill = Person(first_name='Gill',last_name='Jones',partner=None)
>>>> sam = Person(first_name='Sam',last_name='Smith',partner=gill)
>>>> sam.configure_traits()
>>>> gill.configure_traits()
>>>>
>>>>
>>>>
>>> --
>>> Simon Jagoe
>>> Enthought Ltd
>>> [phone]
>>> [hidden email]
>>>
>>
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