# --------------------------------------------------------------------------------------
# Copyright (c) 2013-2023, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
# --------------------------------------------------------------------------------------
from .catom import DefaultValue, Member, Validate
[docs]
class Subclass(Member):
"""A value which allows objects subtypes of a given type.
Values will be tested using the `PyObject_IsSubclass` C API call.
This call is equivalent to `issubclass(value, kind)` and all the
same rules apply.
A Subclass member cannot be set to None.
"""
__slots__ = ()
def __init__(self, kind, default=None):
"""Initialize a Subclass member.
Parameters
----------
kind : type or tuple of types
The allowed type or types for the subclass. This will be
used as the default value if no default is given.
default : type, optional
The default value for the member. If this is not provided,
'kind' will be used as the default.
"""
self.set_default_value_mode(DefaultValue.Static, default or kind)
self.set_validate_mode(Validate.Subclass, kind)
[docs]
class ForwardSubclass(Subclass):
"""A Subclass which delays resolving the type definition.
The first time the value is accessed or modified, the type will
be resolved and the forward subclass will behave identically to
a normal subclass.
"""
__slots__ = "resolve"
def __init__(self, resolve):
"""Initialize a ForwardSubclass member.
resolve : callable
A callable which takes no arguments and returns the type or
tuple of types to use for validating the subclass values.
"""
self.resolve = resolve
self.set_default_value_mode(DefaultValue.MemberMethod_Object, "default")
self.set_validate_mode(Validate.MemberMethod_ObjectOldNew, "validate")
[docs]
def default(self, owner):
"""Called to retrieve the default value.
This is called the first time the default value is retrieved
for the member. It resolves the type and updates the internal
default handler to behave like a normal Subclass member.
"""
kind = self.resolve()
self.set_default_value_mode(DefaultValue.Static, kind)
return kind
[docs]
def validate(self, owner, old, new):
"""Called to validate the value.
This is called the first time a value is validated for the
member. It resolves the type and updates the internal validate
handler to behave like a normal Subclass member.
"""
kind = self.resolve()
self.set_validate_mode(Validate.Subclass, kind)
return self.do_validate(owner, old, new)
[docs]
def clone(self):
"""Create a clone of the ForwardSubclass object."""
clone = super(ForwardSubclass, self).clone()
clone.resolve = self.resolve
return clone