r4695 merged to trunk; trunk now becomes 0.5.

0.4 development continues at /sqlalchemy/branches/rel_0_4

1 files changed, 190 insertions, 0 deletions

diff --git a/examples/custom_attributes/custom_management.py b/examples/custom_attributes/custom_management.py
new file mode 100644
index 000000000..707e182ba
--- /dev/null
+++ b/examples/custom_attributes/custom_management.py
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+"""this example illustrates how to replace SQLAlchemy's class descriptors with a user-defined system.
+
+This sort of thing is appropriate for integration with frameworks that redefine class behaviors
+in their own way, such that SQLA's default instrumentation is not compatible.   
+
+The example illustrates redefinition of instrumentation at the class level as well as the collection
+level, and redefines the storage of the class to store state within "instance._goofy_dict" instead
+of "instance.__dict__".  Note that the default collection implementations can be used 
+with a custom attribute system as well.
+
+"""
+from sqlalchemy import *
+from sqlalchemy.orm import *
+
+from sqlalchemy.orm.attributes import set_attribute, get_attribute, del_attribute, is_instrumented
+from sqlalchemy.orm.collections import collection_adapter
+
+
+class MyClassState(InstrumentationManager):
+    def __init__(self, cls):
+        self.states = {}
+
+    def instrument_attribute(self, class_, key, attr):
+        pass
+
+    def install_descriptor(self, class_, key, attr):
+        pass
+
+    def uninstall_descriptor(self, class_, key, attr):
+        pass
+
+    def instrument_collection_class(self, class_, key, collection_class):
+        return MyCollection
+
+    def get_instance_dict(self, class_, instance):
+        return instance._goofy_dict
+
+    def initialize_instance_dict(self, class_, instance):
+        instance.__dict__['_goofy_dict'] = {}
+
+    def initialize_collection(self, key, state, factory):
+        data = factory()
+        return MyCollectionAdapter(key, state, data), data
+
+    def install_state(self, class_, instance, state):
+        self.states[id(instance)] = state
+
+    def state_getter(self, class_):
+        def find(instance):
+            return self.states[id(instance)]
+        return find
+
+class MyClass(object):
+    __sa_instrumentation_manager__ = MyClassState
+
+    def __init__(self, **kwargs):
+        for k in kwargs:
+            setattr(self, k, kwargs[k])
+
+    def __getattr__(self, key):
+        if is_instrumented(self, key):
+            return get_attribute(self, key)
+        else:
+            try:
+                return self._goofy_dict[key]
+            except KeyError:
+                raise AttributeError(key)
+
+    def __setattr__(self, key, value):
+        if is_instrumented(self, key):
+            set_attribute(self, key, value)
+        else:
+            self._goofy_dict[key] = value
+
+    def __delattr__(self, key):
+        if is_instrumented(self, key):
+            del_attribute(self, key)
+        else:
+            del self._goofy_dict[key]
+
+class MyCollectionAdapter(object):
+    """An wholly alternative instrumentation implementation."""
+    def __init__(self, key, state, collection):
+        self.key = key
+        self.state = state
+        self.collection = collection
+        setattr(collection, '_sa_adapter', self)
+
+    def unlink(self, data):
+        setattr(data, '_sa_adapter', None)
+
+    def adapt_like_to_iterable(self, obj):
+        return iter(obj)
+
+    def append_with_event(self, item, initiator=None):
+        self.collection.add(item, emit=initiator)
+
+    def append_without_event(self, item):
+        self.collection.add(item, emit=False)
+
+    def remove_with_event(self, item, initiator=None):
+        self.collection.remove(item, emit=initiator)
+
+    def remove_without_event(self, item):
+        self.collection.remove(item, emit=False)
+
+    def clear_with_event(self, initiator=None):
+        for item in list(self):
+            self.remove_with_event(item, initiator)
+    def clear_without_event(self):
+        for item in list(self):
+            self.remove_without_event(item)
+    def __iter__(self):
+        return iter(self.collection)
+
+    def fire_append_event(self, item, initiator=None):
+        if initiator is not False and item is not None:
+            self.state.get_impl(self.key).fire_append_event(self.state, item,
+                                                            initiator)
+
+    def fire_remove_event(self, item, initiator=None):
+        if initiator is not False and item is not None:
+            self.state.get_impl(self.key).fire_remove_event(self.state, item,
+                                                            initiator)
+
+    def fire_pre_remove_event(self, initiator=None):
+        self.state.get_impl(self.key).fire_pre_remove_event(self.state,
+                                                            initiator)
+
+class MyCollection(object):
+    def __init__(self):
+        self.members = list()
+    def add(self, object, emit=None):
+        self.members.append(object)
+        collection_adapter(self).fire_append_event(object, emit)
+    def remove(self, object, emit=None):
+        collection_adapter(self).fire_pre_remove_event(object)
+        self.members.remove(object)
+        collection_adapter(self).fire_remove_event(object, emit)
+    def __getitem__(self, index):
+        return self.members[index]
+    def __iter__(self):
+        return iter(self.members)
+    def __len__(self):
+        return len(self.members)
+
+if __name__ == '__main__':
+    meta = MetaData(create_engine('sqlite://'))
+
+    table1 = Table('table1', meta, Column('id', Integer, primary_key=True), Column('name', Text))
+    table2 = Table('table2', meta, Column('id', Integer, primary_key=True), Column('name', Text), Column('t1id', Integer, ForeignKey('table1.id')))
+    meta.create_all()
+
+    class A(MyClass):
+        pass
+
+    class B(MyClass):
+        pass
+
+    mapper(A, table1, properties={
+        'bs':relation(B)
+    })
+
+    mapper(B, table2)
+
+    a1 = A(name='a1', bs=[B(name='b1'), B(name='b2')])
+
+    assert a1.name == 'a1'
+    assert a1.bs[0].name == 'b1'
+    assert isinstance(a1.bs, MyCollection)
+
+    sess = create_session()
+    sess.save(a1)
+
+    sess.flush()
+    sess.clear()
+
+    a1 = sess.query(A).get(a1.id)
+
+    assert a1.name == 'a1'
+    assert a1.bs[0].name == 'b1'
+    assert isinstance(a1.bs, MyCollection)
+
+    a1.bs.remove(a1.bs[0])
+
+    sess.flush()
+    sess.clear()
+
+    a1 = sess.query(A).get(a1.id)
+    assert len(a1.bs) == 1