phaser/src/core/SignalBinding.js

/**
* @author       Richard Davey <rich@photonstorm.com>
* @copyright    2014 Photon Storm Ltd.
* @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/

/**
* @class Phaser.SignalBinding
* @classdesc Object that represents a binding between a Signal and a listener function.
* This is an internal constructor and shouldn't be created directly.
* Inspired by Joa Ebert AS3 SignalBinding and Robert Penner's Slot classes.
*
* @author Miller Medeiros http://millermedeiros.github.com/js-signals/
* @constructor
* @param {Phaser.Signal} signal - Reference to Signal object that listener is currently bound to.
* @param {function} listener - Handler function bound to the signal.
* @param {boolean} isOnce - If binding should be executed just once.
* @param {object} [listenerContext] - Context on which listener will be executed (object that should represent the `this` variable inside listener function).
* @param {number} [priority] - The priority level of the event listener. (default = 0).
*/
Phaser.SignalBinding = function (signal, listener, isOnce, listenerContext, priority) {

    /**
    * @property {Phaser.Game} _listener - Handler function bound to the signal.
    * @private
    */
    this._listener = listener;

    /**
    * @property {boolean} _isOnce - If binding should be executed just once.
    * @private
    */
    this._isOnce = isOnce;

    /**
    * @property {object|undefined|null} context - Context on which listener will be executed (object that should represent the `this` variable inside listener function).
    */
    this.context = listenerContext;

    /**
    * @property {Phaser.Signal} _signal - Reference to Signal object that listener is currently bound to.
    * @private
    */
    this._signal = signal;

    /**
    * @property {number} _priority - Listener priority.
    * @private
    */
    this._priority = priority || 0;

};

Phaser.SignalBinding.prototype = {

    /**
    * If binding is active and should be executed.
    * @property {boolean} active
    * @default
    */
    active: true,

    /**
    * Default parameters passed to listener during `Signal.dispatch` and `SignalBinding.execute` (curried parameters).
    * @property {array|null} params
    * @default
    */
    params: null,

    /**
    * Call listener passing arbitrary parameters.
    * If binding was added using `Signal.addOnce()` it will be automatically removed from signal dispatch queue, this method is used internally for the signal dispatch.
    * @method Phaser.SignalBinding#execute
    * @param {array} [paramsArr] - Array of parameters that should be passed to the listener.
    * @return {any} Value returned by the listener.
    */
    execute: function(paramsArr) {

        var handlerReturn, params;

        if (this.active && !!this._listener)
        {
            params = this.params ? this.params.concat(paramsArr) : paramsArr;
            handlerReturn = this._listener.apply(this.context, params);

            if (this._isOnce)
            {
                this.detach();
            }
        }

        return handlerReturn;

    },

    /**
    * Detach binding from signal.
    * alias to: @see mySignal.remove(myBinding.getListener());
    * @method Phaser.SignalBinding#detach
    * @return {function|null} Handler function bound to the signal or `null` if binding was previously detached.
    */
    detach: function () {
        return this.isBound() ? this._signal.remove(this._listener, this.context) : null;
    },

    /**
    * @method Phaser.SignalBinding#isBound
    * @return {boolean} True if binding is still bound to the signal and has a listener.
    */
    isBound: function () {
        return (!!this._signal && !!this._listener);
    },

    /**
    * @method Phaser.SignalBinding#isOnce
    * @return {boolean} If SignalBinding will only be executed once.
    */
    isOnce: function () {
        return this._isOnce;
    },

    /**
    * @method Phaser.SignalBinding#getListener
    * @return {Function} Handler function bound to the signal.
    */
    getListener: function () {
        return this._listener;
    },

    /**
    * @method Phaser.SignalBinding#getSignal
    * @return {Signal} Signal that listener is currently bound to.
    */
    getSignal: function () {
        return this._signal;
    },

    /**
    * Delete instance properties
    * @method Phaser.SignalBinding#_destroy
    * @private
    */
    _destroy: function () {
        delete this._signal;
        delete this._listener;
        delete this.context;
    },

    /**
    * @method Phaser.SignalBinding#toString
    * @return {string} String representation of the object.
    */
    toString: function () {
        return '[Phaser.SignalBinding isOnce:' + this._isOnce +', isBound:'+ this.isBound() +', active:' + this.active + ']';
    }

};

Phaser.SignalBinding.prototype.constructor = Phaser.SignalBinding;