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""" A type manager. """
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# Enthought library imports.
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from traits.api import HasTraits, Instance, Property, Str
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from abstract_type_system import AbstractTypeSystem
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from adapter_manager import AdapterManager
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from factory import Factory
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from hook import add_pre, add_post, remove_pre, remove_post
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from python_type_system import PythonTypeSystem
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class TypeManager(HasTraits):
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The type manager allows for objects to be created/adapted to a particular
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#### 'TypeManager' interface ##############################################
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# The adapter manager looks after errr, all adapters.
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adapter_manager = Property(Instance(AdapterManager))
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# The type manager's globally unique identifier (only required if you have
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# more than one type manager of course!).
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# The parent type manager.
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# By default this is None, but you can use it to set up a hierarchy of
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# type managers. If a type manager fails to adapt or create an object of
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# some target class then it will give its parent a chance to do so.
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parent = Instance('TypeManager')
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# The type system used by the manager (it determines 'is_a' relationships
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# By default we use standard Python semantics.
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type_system = Instance(AbstractTypeSystem, PythonTypeSystem())
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#### Private interface ####################################################
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# The adapter manager looks after errr, all adapters.
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_adapter_manager = Instance(AdapterManager)
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###########################################################################
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# 'TypeManager' interface.
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###########################################################################
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#### Properties ###########################################################
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def _get_adapter_manager(self):
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""" Returns the adapter manager. """
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return self._adapter_manager
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#### Methods ##############################################################
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def object_as(self, obj, target_class, *args, **kw):
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""" Adapts or creates an object of the target class.
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Returns None if no appropriate adapter or factory is available.
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# If the object is already an instance of the target class then we
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if self.type_system.is_a(obj, target_class):
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# If the object is a factory that creates instances of the target class
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# then ask it to produce one.
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elif self._is_factory_for(obj, target_class, *args, **kw):
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result = obj.create(target_class, *args, **kw)
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# Otherwise, see if the object can be adapted to the target class.
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result = self._adapter_manager.adapt(obj, target_class, *args,**kw)
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# If this type manager couldn't do the job, then give its parent a go!
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if result is None and self.parent is not None:
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result = self.parent.object_as(obj, target_class, *args, **kw)
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def register_adapters(self, factory, adaptee_class):
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""" Registers an adapter factory.
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'adaptee_class' can be either a class or the name of a class.
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self._adapter_manager.register_adapters(factory, adaptee_class)
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def unregister_adapters(self, factory):
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""" Unregisters an adapter factory. """
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self._adapter_manager.unregister_adapters(factory)
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def register_instance_adapters(self, factory, obj):
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""" Registers an adapter factory for an individual instance.
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A factory can be in exactly one manager (as it uses the manager's type
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self._adapter_manager.register_instance_adapters(factory, obj)
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def unregister_instance_adapters(self, factory, obj):
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""" Unregisters an adapter factory for an individual instance.
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A factory can be in exactly one manager (as it uses the manager's type
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self._adapter_manager.unregister_instance_adapters(factory, obj)
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def register_type_adapters(self, factory, adaptee_class):
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""" Registers an adapter factory.
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'adaptee_class' can be either a class or the name of a class.
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self._adapter_manager.register_type_adapters(factory, adaptee_class)
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def unregister_type_adapters(self, factory):
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""" Unregisters an adapter factory. """
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self._adapter_manager.unregister_type_adapters(factory)
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# Currently, there is no technical reason why we have this convenience
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# method to add categories. However, it may well turn out to be useful to
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# track all categories added via the type manager.
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def add_category(self, klass, category_class):
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""" Adds a category to a class. """
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klass.add_trait_category(category_class)
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# Currently, there is no technical reason why we have these convenience
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# methods to add and remove hooks. However, it may well turn out to be
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# useful to track all hooks added via the type manager.
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def add_pre(self, klass, method_name, callable):
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""" Adds a pre-hook to method 'method_name' on class 'klass. """
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add_pre(klass, method_name, callable)
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def add_post(self, klass, method_name, callable):
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""" Adds a post-hook to method 'method_name' on class 'klass. """
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add_post(klass, method_name, callable)
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def remove_pre(self, klass, method_name, callable):
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""" Removes a pre-hook to method 'method_name' on class 'klass. """
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remove_pre(klass, method_name, callable)
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def remove_post(self, klass, method_name, callable):
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""" Removes a post-hook to method 'method_name' on class 'klass. """
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remove_post(klass, method_name, callable)
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###########################################################################
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###########################################################################
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#### Initializers #########################################################
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def __adapter_manager_default(self):
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""" Initializes the '_adapter_manager' trait. """
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return AdapterManager(type_system=self.type_system)
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#### Methods ##############################################################
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def _is_factory_for(self, obj, target_class, *args, **kw):
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""" Returns True iff the object is a factory for the target class. """
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is_factory_for = self.type_system.is_a(obj, Factory) \
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and obj.can_create(target_class, *args, **kw)
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return is_factory_for
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#### EOF ######################################################################
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apptools/type_manager/type_manager.py
