michael@0: /* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsISupports.idl"
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * An instance of |nsIWeakReference| is a proxy object that cooperates with
michael@0:  * its referent to give clients a non-owning, non-dangling reference.  Clients
michael@0:  * own the proxy, and should generally manage it with an |nsCOMPtr| (see the
michael@0:  * type |nsWeakPtr| for a |typedef| name that stands out) as they would any
michael@0:  * other XPCOM object.  The |QueryReferent| member function provides a
michael@0:  * (hopefully short-lived) owning reference on demand, through which clients
michael@0:  * can get useful access to the referent, while it still exists.
michael@0:  *
michael@0:  * @version 1.0
michael@0:  * @see nsISupportsWeakReference
michael@0:  * @see nsWeakReference
michael@0:  * @see nsWeakPtr
michael@0:  */
michael@0: [scriptable, uuid(9188bc85-f92e-11d2-81ef-0060083a0bcf)]
michael@0: interface nsIWeakReference : nsISupports
michael@0:   {
michael@0:     /**
michael@0:      * |QueryReferent| queries the referent, if it exists, and like |QueryInterface|, produces
michael@0:      * an owning reference to the desired interface.  It is designed to look and act exactly
michael@0:      * like (a proxied) |QueryInterface|.  Don't hold on to the produced interface permanently;
michael@0:      * that would defeat the purpose of using a non-owning |nsIWeakReference| in the first place.
michael@0:      */
michael@0:     void QueryReferent( in nsIIDRef uuid, [iid_is(uuid), retval] out nsQIResult result );
michael@0:   };
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * |nsISupportsWeakReference| is a factory interface which produces appropriate
michael@0:  * instances of |nsIWeakReference|.  Weak references in this scheme can only be
michael@0:  * produced for objects that implement this interface.
michael@0:  *
michael@0:  * @version 1.0
michael@0:  * @see nsIWeakReference
michael@0:  * @see nsSupportsWeakReference
michael@0:  */
michael@0: [scriptable, uuid(9188bc86-f92e-11d2-81ef-0060083a0bcf)]
michael@0: interface nsISupportsWeakReference : nsISupports
michael@0:   {
michael@0:     /**
michael@0:      * |GetWeakReference| produces an appropriate instance of |nsIWeakReference|.
michael@0:      * As with all good XPCOM `getters', you own the resulting interface and should
michael@0:      * manage it with an |nsCOMPtr|.
michael@0:      *
michael@0:      * @see nsIWeakReference
michael@0:      * @see nsWeakPtr
michael@0:      * @see nsCOMPtr
michael@0:      */
michael@0:     nsIWeakReference GetWeakReference();
michael@0:   };
michael@0: 
michael@0: 
michael@0: %{C++
michael@0: #ifdef MOZILLA_INTERNAL_API
michael@0: #include "nsIWeakReferenceUtils.h"
michael@0: #endif
michael@0: %}
michael@0: