nsISupportsWeakReference
remarks the xpcom glue library provides nssupportsweakreference, a canonical implementation of nsisupportsweakreference.

Weak reference
the following assumes that any nsiobserver that is passed in also implements nsisupportsweakreference.
... in javascript, just make sure that your queryinterface method returns your object for the nsisupportsweakreference interface, and you're set; xpconnect does all the work for you.
... ns_interface_map_entry(nsisupportsweakreference) // ...
...And 2 more matches

nsSupportsWeakReference
« xpcom api reference summary inherit from this c++ class to add canonical support for nsisupportsweakreference.
...}; remarks in addition to inheriting from this class, you will need to ensure that your nsisupports::queryinterface implementation exposes nsisupportsweakreference as a supported interface.
... }; ns_impl_isupports2(myfoo, nsifoo, nsisupportsweakreference) ...
... see also nsisupports::queryinterface , nsisupportsweakreference ...

Index
990 nsisupportsweakreference interfaces, interfaces:scriptable, xpcom, xpcom api reference, xpcom interface reference produces an appropriate instance of nsiweakreference.
... 991 getweakreference this content is now available at nsisupportsweakreference.getweakreference().
...ing class declaration 1224 nsstring external needscontent, reference, référence(2), strings class declaration 1225 nsstringcontainer (external) needscontent, reference, référence(2), strings class declaration 1226 nssupportsweakreference xpcom, xpcom api reference inherit from this c++ class to add canonical support for nsisupportsweakreference.

Progress Listeners - Archive of obsolete content
example create an object which implements nsiwebprogresslistener: const state_start = ci.nsiwebprogresslistener.state_start; const state_stop = ci.nsiwebprogresslistener.state_stop; var mylistener = { queryinterface: xpcomutils.generateqi(["nsiwebprogresslistener", "nsisupportsweakreference"]), onstatechange: function(awebprogress, arequest, aflag, astatus) { // if you use mylistener for more than one tab/window, use // awebprogress.domwindow to obtain the tab/window which triggers the state change if (aflag & state_start) { // this fires when the load event is initiated } if (aflag & state_stop) { // this fires wh...
... alert(auri.spec); this.oldurl = auri.spec; }, // nsiwebprogresslistener queryinterface: xpcomutils.generateqi(["nsiwebprogresslistener", "nsisupportsweakreference"]), onlocationchange: function(aprogress, arequest, auri) { this.processnewurl(auri); }, onstatechange: function() {}, onprogresschange: function() {}, onstatuschange: function() {}, onsecuritychange: function() {} }; window.addeventlistener("load", function() { myextension.init() }, false); window.addeventlistener("unload", function() { myextension.uninit() }, ...

Component; nsIPrefBranch
the object must implement the nsisupportsweakreference interface or this will fail.
...there are 3 approaches which have been implemented in an attempt to avoid these situations: the nsprefbranch object supports nsisupportsweakreference.

nsIPrefBranch2
the object must implement the nsisupportsweakreference interface or this will fail.
...there are 3 approaches which have been implemented in an attempt to avoid these situations: the nsprefbranch object supports nsisupportsweakreference.

XUL Questions and Answers - Archive of obsolete content
rowser" to a listener object browserobject.addprogresslistener( listobj, components.interfaces.nsiwebprogress.notify_state_window ); // remember to define the object, something like this: listobj = new object(); listobj.wpl = components.interfaces.nsiwebprogresslistener; listobj.queryinterface = function(aiid) { if (aiid.equals(listobj.wpl) || aiid.equals(components.interfaces.nsisupportsweakreference) || aiid.equals(components.interfaces.nsisupports)) return this; throw components.results.ns_nointerface; } listobj.onstatechange = function(aprogress, arequest, aflag, astatus) { if (aflag & listobj.wpl.state_start) { // this fires when the load event is initiated } else { if (aflag & listobj.wpl.state_stop) { if ( aflag & listobj.wpl.state_is_window ) { // ...

XULBrowserWindow - Archive of obsolete content
in order to do so it implements the following interfaces: nsisupports nsixulbrowserwindow nsiwebprogresslistener nsiwebprogresslistener2 nsisupportsweakreference note: this page is not complete at this time.

JavaScript Tips
however, in javascript this is quite simple even in the case of a weak reference which in c++ requires a helper class: var weakobserver = { queryinterface: function queryinterface(aiid) { if (aiid.equals(components.interfaces.nsiobserver) || aiid.equals(components.interfaces.nsisupportsweakreference) || aiid.equals(components.interfaces.nsisupports)) return this; throw components.results.ns_nointerface; }, observe: function observe(asubject, atopic, astate) { } } when declaring xpcom methods, try to use the same names for method parameters as are used in the interface definition.

XPCOM glue classes
this is done using the functions addref() and release(), which respectively modify a variable of type nsautorefcnt, which basically is a wrapper around a count of the number of references refering to the class.nsstringclass declarationnsstring externalclass declarationnsstringcontainer (external)class declarationnssupportsweakreferenceinherit from this c++ class to add canonical support for nsisupportsweakreference.nsxpidlcstringclass declarationnsxpidlstringclass declarationpromiseflatcstring (external)class declarationpromiseflatstring (external)class declaration ...

nsINavBookmarksService
if ownsweak is true, then aobserver must implement nsisupportsweakreference, and the bookmark service will keep a weak reference to the observer.

nsINavHistoryResult
if true, the result will keep a weak reference to the observer, which must implement the nsisupportsweakreference interface.

nsINavHistoryService
if ownsweak is true, then aobserver must implement nsisupportsweakreference, and the history service will keep a weak reference to the observer.

nsIObserverService
if set to true and anobserver supports the nsisupportsweakreference interface, a weak reference will be held.