author | andy simpson <andrews@symbian.org> |
Fri, 08 Oct 2010 16:52:59 +0100 | |
changeset 119 | 931f2bbaabf7 |
parent 1 | 2fb8b9db1c86 |
permissions | -rw-r--r-- |
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.. highlightlang:: c |
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.. _weakrefobjects: |
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Weak Reference Objects |
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---------------------- |
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Python supports *weak references* as first-class objects. There are two |
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specific object types which directly implement weak references. The first is a |
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simple reference object, and the second acts as a proxy for the original object |
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as much as it can. |
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.. cfunction:: int PyWeakref_Check(ob) |
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Return true if *ob* is either a reference or proxy object. |
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.. versionadded:: 2.2 |
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.. cfunction:: int PyWeakref_CheckRef(ob) |
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Return true if *ob* is a reference object. |
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.. versionadded:: 2.2 |
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.. cfunction:: int PyWeakref_CheckProxy(ob) |
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Return true if *ob* is a proxy object. |
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.. versionadded:: 2.2 |
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.. cfunction:: PyObject* PyWeakref_NewRef(PyObject *ob, PyObject *callback) |
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Return a weak reference object for the object *ob*. This will always return |
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a new reference, but is not guaranteed to create a new object; an existing |
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reference object may be returned. The second parameter, *callback*, can be a |
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callable object that receives notification when *ob* is garbage collected; it |
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should accept a single parameter, which will be the weak reference object |
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itself. *callback* may also be ``None`` or *NULL*. If *ob* is not a |
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weakly-referencable object, or if *callback* is not callable, ``None``, or |
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*NULL*, this will return *NULL* and raise :exc:`TypeError`. |
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.. versionadded:: 2.2 |
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.. cfunction:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback) |
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Return a weak reference proxy object for the object *ob*. This will always |
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return a new reference, but is not guaranteed to create a new object; an |
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existing proxy object may be returned. The second parameter, *callback*, can |
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be a callable object that receives notification when *ob* is garbage |
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collected; it should accept a single parameter, which will be the weak |
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reference object itself. *callback* may also be ``None`` or *NULL*. If *ob* |
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is not a weakly-referencable object, or if *callback* is not callable, |
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``None``, or *NULL*, this will return *NULL* and raise :exc:`TypeError`. |
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.. versionadded:: 2.2 |
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.. cfunction:: PyObject* PyWeakref_GetObject(PyObject *ref) |
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Return the referenced object from a weak reference, *ref*. If the referent is |
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no longer live, returns ``None``. |
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.. versionadded:: 2.2 |
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.. cfunction:: PyObject* PyWeakref_GET_OBJECT(PyObject *ref) |
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Similar to :cfunc:`PyWeakref_GetObject`, but implemented as a macro that does no |
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error checking. |
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.. versionadded:: 2.2 |