Mediator

mediator01.js

var mediator = (function(){
    var subscribe = function(channel, fn){
        if (!mediator.channels[channel]) mediator.channels[channel] = [];
        mediator.channels[channel].push({ context: this, callback: fn });
        return this;
    },
 
    publish = function(channel){
        if (!mediator.channels[channel]) return false;
        var args = Array.prototype.slice.call(arguments, 1);
        for (var i = 0, l = mediator.channels[channel].length; i < l; i++) {
            var subscription = mediator.channels[channel][i];
            subscription.callback.apply(subscription.context, args);
        }
        return this;
    };
 
    return {
        channels: {},
        publish: publish,
        subscribe: subscribe,
        installTo: function(obj){
            obj.subscribe = subscribe;
            obj.publish = publish;
        }
    };
 
}());

//Pub/sub on a centralized mediator
 
mediator.name = "tim";
mediator.subscribe('nameChange', function(arg){
        console.log(this.name);
        this.name = arg;
        console.log(this.name);
});
 
mediator.publish('nameChange', 'david'); //tim, david
 
 
//Pub/sub via third party mediator
 
var obj = { name: 'sam' };
mediator.installTo(obj);
obj.subscribe('nameChange', function(arg){
        console.log(this.name);
        this.name = arg;
        console.log(this.name);
});
 
obj.publish('nameChange', 'john'); //sam, john

mediator02.js

Mediator = function() {
        
        var debug = function() {
            // console.log or air.trace as desired
        };
        
        var components = {};
        
        var broadcast = function(event, args, source) {
            if (!event) {
                return;
            }
            args = args || [];
            //debug(["Mediator received", event, args].join(' '));
            for (var c in components) {
                if (typeof components[c]["on" + event] == "function") {
                    try {
                        //debug("Mediator calling " + event + " on " + c);
                        source = source || components[c];
                        components[c]["on" + event].apply(source, args);
                    } catch (err) {
                        debug(["Mediator error.", event, args, source, err].join(' '));
                    }
                }
            }
        };
        
        var addComponent = function(name, component, replaceDuplicate) {
            if (name in components) {
                if (replaceDuplicate) {
                    removeComponent(name);
                } else {
                    throw new Error('Mediator name conflict: ' + name);
                }
            }
            components[name] = component;
        };
        
        var removeComponent = function(name) {
            if (name in components) {
                delete components[name];
            }
        };
        
        var getComponent = function(name) {
            return components[name]; // undefined if component has not been added
        };
        
        var contains = function(name) {
            return (name in components);
        };
        
        return {
            name      : "Mediator",
            broadcast : broadcast,
            add       : addComponent,
            rem       : removeComponent,
            get       : getComponent,
            has       : contains
        };
    }();
    
    
    // Using
    Mediator.add('TestObject', function() {
        
        var someNumber = 0; // sample variable
        var someString = 'another sample variable';
        
        return {
            onInitialize: function() {
                // this.name is automatically assigned by the Mediator
                alert(this.name + " initialized.");
            },
            onFakeEvent: function() {
                someNumber++;
                alert("Handled " + someNumber + " times!");
            },
            onSetString: function(str) {
                someString = str;
                alert('Assigned ' + someString);
            }
        }
    }());
    Mediator.broadcast("Initialize");                 // alerts "TestObject initialized"
    Mediator.broadcast('FakeEvent');                  // alerts "Handled 1 times!" (I know, bad grammar)
    Mediator.broadcast('SetString', ['test string']); // alerts "Assigned test string"
    Mediator.broadcast('FakeEvent');                  // alerts "Handled 2 times!"
    Mediator.broadcast('SessionStart');               // this call is safely ignored
    Mediator.broadcast('Translate', ['this is also safely ignored']);