Please note: this project is inactive since early 2006
4.7.1 Finalizing an EditingContext: breaking reference cycles
When an EditingContext is about to be deleted, its
dispose() method gets called.
This is followed with a two-step procedure, acting on each object registered
within the EditingContext:
- Un-registered:
Each object held by the EC is unregistered and detached, and, if no other
reference to that object exists, it will thus be ready to be garbage
collected - however, other objects in the EditingContext are likely
to hold a reference to it especially if your model defines relationships
between objects (see below). From this point on,
obj.editingContext()
returns None.
- Invalidated:
Then, depending on the value returned by
invalidatesObjectsWhenFinalized():
-
If true, then the object receives the message
clearProperties, defined in DatabaseObject, which empties
its __dict__ - this is called invalidating the object.
-
otherwise, no further action is taken.
The default behaviour for an EditingContext is to invalidate its
objects. The reason for this is that the objects you fetch or create within
an EditingContext are most of the time in relation with each other;
these relations tend to create reference cycles between them, hence making
it harder for the garbage collection to notice they are not referenced
anymore. Invalidating each object actually breaks the reference cycles which
helps the garbage collecter to detect that they should be destroyed.
Comments are welcome: Sebastien Bigaret / Modeling Home Page
Hosted by:
