Created
July 8, 2011 20:01
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Create a singleton class in YUI3. This class can only be instantiated one time. All later instantiations return references to the original.
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YUI().use("singleton-class", function (Y) { | |
var instance1 = new Y.SingletonClass(), | |
instance2 = new Y.SingletonClass(); | |
Y.log(instance1 === instance2); // true! | |
window.instance1 = instance1; | |
}); | |
YUI().use("singleton-class", function (Y) { | |
var instance3 = new Y.SingletonClass(); | |
Y.log(window.instance1 === instance3); // true! | |
}); |
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YUI.add("singleton-class", function (Y) { | |
var GlobalEnv, SingletonClass, instanceMethods, classMethods; | |
// create your own namespace in the YUI global environment | |
GlobalEnv = YUI.namespace("Env.SingletonClassNamespace"); | |
// define the singleton class | |
SingletonClass = function (confg) { | |
// if an instance doesn't exist yet | |
// do the normal class initialization and set the global | |
// instance to this instance | |
if (Y.Lang.isUndefined(GlobalEnv.instance)) { | |
SingletonClass.superclass.constructor.apply(this, arguments); | |
GlobalEnv.instance = this; | |
} | |
// instead of returning this, return the global instance | |
return GlobalEnv.instance; | |
}; | |
// expose your singleton class to the world | |
Y.SingletonClass = SingletonClass; | |
// if an instance of the class already exists, you don't | |
// even need to do anything else. This doesn't | |
// work if your application relies on class methods, so | |
// only uncomment this if adding instance and class methods | |
// to your class is expensive (it's probably not). | |
// | |
// if (! Y.Lang.isUndefined(GlobalEnv.instance)) { | |
// return; | |
// } | |
// add your instance methods with at least these two defined | |
instanceMethods = { | |
initializer: function (config) {}, | |
destructor: function () {} | |
}; | |
// add your class methods with the NAME and ATTRS properties | |
classMethods = { | |
NAME: "singleton-class", | |
ATTRS: { | |
foo: { | |
value: "bar" | |
} | |
} | |
}; | |
// add instance methods, class methods and attrs by extending Y.Base | |
Y.extend(SingletonClass, Y.Base, instanceMethods, classMethods); | |
}, "3.3.0", { requires: ["base-base"] }); |
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