The Init Method
There is another alternative to using the init object as a means of providing your class constructor with variable arguments. That alternative is to essentially not use the constructor at all and instead opt to construct or initiate your object through, not the constructor, but a separate method call directly following attachMovie. This method is often called the init method.

The init method for movieclip classes are methods but take on the responsibilities of constructor functions. It not only allows you to have a constructor-like operation with optional passed parameters, but also gives you a way to re-construct or re-initialize an object through a method, as though redefining an instance from scratch. That alone may be reason enough to use this technique with other classes as well.

As a method, though, init will need to be called manually, adding what otherwise would be an extra step in movieclip creation. We can see its use by incorporating it into the Helper example.
 

Helper = function(){

// constructor not used in favor of init

};

Helper.prototype = new MovieClip();

Helper.prototype.init = function(status){

if (status == "inactive"){

this._alpha = 50;

}

};

Object.registerClass("helperClip", Helper);

 

screenStatus = "inactive";

this.attachMovie("helperClip", "helper1", 1);

helper1.init(screenStatus);

trace(helper1._alpha); // traces 50

The constructor is still run – its run automatically – but it has no purpose now. The constructor responsibilities are carried over to the init method. Being a method called after the creation of the object, it can have any argument passed to it you wish just as though it were any other constructor call.

If you want, you can even compact its use a little by tacking init right on the end of the attachMovie call. In doing this, just be sure to return this in the init call so that you are still able to assign variables to reference the movieclip in the call.

Helper = function(){};

Helper.prototype = new MovieClip();

Helper.prototype.init = function(status){

if (status == "inactive"){

this._alpha = 50;

}

return this;

};

Object.registerClass("helperClip", Helper);

 

screenStatus = "inactive";

this.attachMovie("helperClip", "helper1", 1).init(screenStatus);

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