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The SignalManager is a convenience object for managing signals. If you use this to connect signals, you can later disconnect them by signal name or just disconnect everything! No need to keep track of those annoying signalIds by yourself anymore!
A common use case is to use the SignalManager to connect to signals and then use the disconnectAllSignals function when the object is destroyed, to avoid keeping track of all the signals manually.
However, this is not always needed. If you are connecting to a signal of your actor, the signals are automatically disconnected when you destroy the actor. Using the SignalManager to disconnect all signals is only needed when connecting to objects that persists after the object disappears.
Every Javascript object should have its own SignalManager, and use it to connect signals of all objects it takes care of. For example, the panel will have one SignalManger object, which manages all signals from GSettings, global.screen etc.
An example usage is as follows:
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MyApplet.prototype = { __proto__: Applet.Applet.prototype, _init: function(orientation, panelHeight, instanceId) { Applet.Applet.prototype._init.call(this, orientation, panelHeight, instanceId); this._signalManager = new SignalManager.SignalManager(this); this._signalManager.connect(global.settings, "changed::foo", this._onChanged); }, _onChanged: function() { // Do something }, on_applet_removed_from_panel: function() { this._signalManager.disconnectAllSignals(); } } |
connect (Object obj,string sigName,function callback,Object bind,boolean force);
This listens to the signal sigName from obj and calls callback when the signal is emitted. callback is automatically binded to this._object, unless the bind argument is set to something else, in which case the function will be binded to bind.
This checks whether the signal is already connected and will not connect again if it is already connected. This behaviour can be overridden by settings force to be true.
For example, what you would normally write as
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global.settings.connect("changed::foo", Lang.bind(this, this._bar)) |
would become
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this._signalManager.connect(global.settings, "changed::foo", this._bar) |
Note that in this function, the first argument is the object, while the second is the signal name. In all other methods, you first pass the signal name, then the object (since the object is rarely passed in other functions).
obj |
the object whose signal we are listening to |
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sigName |
the name of the signal we are listening to |
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callback |
the callback function |
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bind |
(optional) the object to bind the function to. Leave empty for the owner of the |
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force |
whether to connect again even if it is connected |
isConnected (string sigName,Object obj,function callback);
This checks whether the signal sigName is connected. The optional arguments obj and callback can be used to specify what signals in particular we want to know. Note that when you supply callBack, you usually want to supply obj as well, since two different objects can connect to the same signal with the same callback.
disconnect (string sigName,Object obj,function callback);
This disconnects all signals named sigName. By default, it disconnects the signal on all objects, but can be fine-tuned with the optional obj and callback arguments.
This function will do nothing if no such signal is connected, the object no longer exists, or the signal is somehow already disconnected. So checks need not be performed before calling this function.
disconnectAllSignals ();
Disconnects all signals managed by the SignalManager. This is useful in the destroy function of objects.
“_object” Object
The object owning the SignalManager. All callbacks are binded to _object unless otherwise specified.