How do I define the contents of a Traits/UI View programmatically?

Question

I have a case in which I don't know the required contents (i.e. - set of Traits) of a HasTraits subclass, until program run time, because it depends upon the result of parsing a certain file with variable contents.

How can I customize the View for this HasTraits subclass programmatically, just before calling its configure_traits() method?

Here is a simple test case, which illustrates the problem:

#! /usr/bin/env python

'Test case, showing problem with dynamically constructed view.'

from traits.api   import HasTraits
from traitsui.api import View, Item

class DynamicViewTester(HasTraits):
    'Tries to dynamically construct its View, using default_traits_view().'

    def default_traits_view(self):
        view = View(
            Item(label='Hello, World!'),
            title='Dynamically Assembled View',
        )
        view.add_trait('msg', Item(label='Goodbye, World.'))
        return view

if(__name__ == '__main__'):
    DynamicViewTester().configure_traits()

When I run this code, I only see the "Hello, World!" message in the resultant GUI. I do NOT see the "Goodbye, World." message.

Answer 1

I found a solution:

#! /usr/bin/env python

'Test case, showing solution to dynamically constructed view problem.'

from traits.api   import HasTraits, String
from traitsui.api import View, Item

class DynamicViewTester(HasTraits):
    'Dynamically construct its View, using default_traits_view().'

    def __init__(self, *args, **traits):
        super(DynamicViewTester, self).__init__(*args, **traits)

        # Here is where I'll parse the input file, constructing 'content' accordingly.
        content = []
        content.append(Item(label='Hello, World!'))
        content.append(Item(label='Goodbye, World.'))

        self._content = content

    def default_traits_view(self):
        view = View(
            title='Dynamically Assembled View',
            height=0.4,
            width=0.4,
        )
        view.set_content(self._content)
        return view

if(__name__ == '__main__'):
    DynamicViewTester().configure_traits()