Creating Instances from the Library with Strings

Ben — Sun, 20 Dec 2009 18:52:25 +0000

Problem: while working on an AS3 document you uncover an unusual situation in which you have a string class name that corresponds to something in the library. How does one do it?

I’ve come across this a number of times and found myself dropboxing this snippet so I would always have it with me …

import flash.utils.*;

/** 

 * Takes a string classname, returns an instance of that class, if it exists. 

 */

private function newInstanceFromString(className:String):*{

    try{ 

        var classRef:Class = getDefinitionByName(className) as Class; 

        return new classRef();

    } catch( e:ReferenceError ){

        trace('Error: there was a problem creating an instance of the "'+className+'" class. Check your library and linkage to ensure it\'s there.');

        trace(e+"\n"); 

    }

}

See the AS3 livedocs for more information about getDefinitionByName, the super helpful method that makes it all work.

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Creating Instances from the Library with Strings