问题
I would like to wrap a non-Traits model class for use with Python Traits. My goal is to write a Traits-based UI to manipulate an "external" model class. The external model class has been generated by SWIG and so I cannot add enthought.traits.api.HasTraits as an ancestor (I think, though I may be wrong).
My current best attempt is
from enthought.traits.api import HasStrictTraits, Property, Instance
class ExternalModel():
foo = 'foo'
class TraitsModel(HasStrictTraits):
_e = Instance(ExternalModel)
def __init__(self):
self._e = ExternalModel()
self.add_trait('foo', Property(lambda :getattr(self._e,'foo' ),
lambda attr:setattr(self._e,'foo',attr)))
which causes the Traits-based class TraitsModel to have a mutable property which delegates to the contained non-Traits ExternalModel instance. However, TraitsModel.trait_names() doesn't report 'foo' as a recognized trait.
Any suggestions for how to have TraitsModel report a 'foo' trait which is linked to ExternalModel? enthought.traits.api.DelegatesTo seems to require the target be a Traits class (though I may not have found the right invocation and that is possible).
A more MVC-ish approach is probably to have a Traits-based view of my ExternalModel. I've been unable to figure out having a non-Traits model for a Traits-based view. Suggestions in that direction also greatly welcome.
Update I have figured out how to get HasTraits as the ExternalModel superclass using the approach at http://agentzlerich.blogspot.com/2011_05_01_archive.html and it seems to have been a complete waste of time. Apparently the SWIG voodoo and the Traits hoodoo do not jive. Wrapping ExternalModel within TraitsModel as this question asks seems the best route.
回答1:
from enthought.traits.api import HasStrictTraits, Instance, Property
class ExternalModel(object):
foo = 'foo'
class TraitsModel(HasStrictTraits):
_e = Instance(ExternalModel, ExternalModel())
def __init__(self):
'''
>>> wrapper = TraitsModel()
>>> wrapper.foo
'foo'
>>> wrapper._e.foo = 'bar'
>>> wrapper.foo
'bar'
>>> wrapper.trait_names()
['trait_added', '_e', 'foo', 'trait_modified']
'''
HasStrictTraits.__init__(self)
for trait in (name for name in dir(self._e) if not name.startswith('__')):
self.__class__.add_class_trait(
trait,
Property(
lambda:getattr(self._e, trait),
lambda attr:setattr(self._e, trait, attr)
)
)
if __name__ == '__main__':
import doctest
doctest.testmod()
A fairly robust solution is to use the add_class_trait of the HasTraits
class, coupled with dir(self._e)
to get the names of the class attributes of ExternalModel
and a generator expression/list comprehension to filter the magic class method names (filter
with an appropriate function would work better for wrapping a more complex class).
Also:
ExternalModel
should inherit fromobject
__init__
should callHasStrictTraits.__init__
(orsuper(HasStrictTraits, self).__init__()
)_e
can also be created in the Instance trait declaration as the second argument usingExternalModel()
or even()
, or as a method of TraitsModel like:def __e_default(self): # note preceding underscore return ExternalModel()
Lastly, I have an slightly old copy of the Enthought APIs including Traits which can be very handy.
来源:https://stackoverflow.com/questions/6113822/how-can-i-wrap-a-non-traits-model-for-use-with-python-traits