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TraitType -> BaseDescriptor, and replace call to set_default_value with instance_init #26

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Jun 4, 2015
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TraitType -> BaseDescriptor, and replace call to set_default_value with instance_init #26

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6e76756
TraitType -> BaseDescriptor
SylvainCorlay Jun 4, 2015
39782c3
add_trait should call instance_init, not set_default_value
SylvainCorlay Jun 4, 2015
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36 changes: 8 additions & 28 deletions traitlets/traitlets.py
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Original file line number Diff line number Diff line change
Expand Up @@ -377,10 +377,8 @@ def get_default_value(self):
def init_default_value(self, obj):
"""Instantiate the default value for the trait type.

This method is called by :meth:`TraitType.set_default_value` in the
case a default value is provided at construction time or later when
accessing the trait value for the first time in
:meth:`HasTraits.__get__`.
This method is called when accessing the trait value for the first
time in :meth:`HasTraits.__get__`.
"""
value = self.get_default_value()
value = self._validate(obj, value)
Expand All @@ -401,23 +399,6 @@ def _setup_dynamic_initializer(self, obj):
obj._trait_dyn_inits[self.name] = meth_name
return True

def set_default_value(self, obj):
"""Set the default value on a per instance basis.

This method is called by :meth:`HasTraits.__new__` to instantiate and
validate the default value. The creation and validation of
default values must be delayed until the parent :class:`HasTraits`
class has been instantiated.
Parameters
----------
obj : :class:`HasTraits` instance
The parent :class:`HasTraits` instance that has just been
created.
"""
if not self._setup_dynamic_initializer(obj):
# We didn't find a dynamic initializer. Do static initialization.
self.init_default_value(obj)

def _set_default_value_at_instance_init(self, obj):
# As above, but if no default was specified, don't try to set it.
# If the trait is accessed before it is given a value, init_default_value
Expand Down Expand Up @@ -451,8 +432,7 @@ def __get__(self, obj, cls=None):
else:
return self.init_default_value(obj)
except Exception:
# HasTraits should call set_default_value to populate
# this. So this should never be reached.
# This should never be reached.
raise TraitError('Unexpected error in TraitType: '
'default value not set properly')
else:
Expand Down Expand Up @@ -551,11 +531,11 @@ def __new__(mcls, name, bases, classdict):
def __init__(cls, name, bases, classdict):
"""Finish initializing the HasTraits class.

This sets the :attr:`this_class` attribute of each TraitType in the
This sets the :attr:`this_class` attribute of each BaseDescriptor in the
class dict to the newly created class ``cls``.
"""
for k, v in iteritems(classdict):
if isinstance(v, TraitType):
if isinstance(v, BaseDescriptor):
v.this_class = cls
super(MetaHasTraits, cls).__init__(name, bases, classdict)

Expand Down Expand Up @@ -865,11 +845,11 @@ def trait_metadata(self, traitname, key, default=None):
else:
return trait.get_metadata(key, default)

def add_trait(self, traitname, trait):
def add_trait(self, name, trait):
"""Dynamically add a trait attribute to the HasTraits instance."""
self.__class__ = type(self.__class__.__name__, (self.__class__,),
{traitname: trait})
trait.set_default_value(self)
{name: trait})
trait.instance_init(self)

#-----------------------------------------------------------------------------
# Actual TraitTypes implementations/subclasses
Expand Down