Dynamically adding a trait with UI update

Question

Is it possible in a configure_traits() window to have a button like 'Add integer' on which clicking will add a new integer field ready for edition in the same window?

Answer 1

As @jonathan-march points out, it would probably be safest if you only need a fixed number of fields to keep them hidden until you clicked the button, but if you need an indeterminate number, it's fairly trivial to make a List of Ints and then append to that list each time you click the button. The trouble will be in the book-keeping that comes with keeping track of the indices of those list elements when you want to listen to them. I whipped up a small example of how you might do this below:

from traits.api import Button, HasStrictTraits, Int, List
from traitsui.api import Group, Item, ListEditor, UItem, View


class DynamicListOfInts(HasStrictTraits):

    integer_list = List(Int)
    add_int = Button('Add integer')

    def default_traits_view(self):
        view = View(
            Group(
                UItem('add_int'),
                Item('integer_list', editor=ListEditor()),
            ),
            width=300,
            height=500,
        )
        return view

    def _add_int_changed(self):
        self.integer_list.append(0)


if __name__ == '__main__':
    list_of_ints = DynamicListOfInts()
    list_of_ints.configure_traits()