Understanding AS3 getDefinitionByName (for all eval maniacs)

Understanding AS3 getDefinitionByName (for all eval maniacs):

Sometimes you may want to create a new class or DisplayObject only starting from its name. This is where something like an eval function would come into play, but we have to manage it in a different way with AS3.

Look at this movie:

Circles are four different objects called symbol1, symbol2, symbol3 and symbol4 and this is the script:

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package { import flash.display.Sprite; public class Main extends Sprite { public function Main() { var s1:symbol1=new symbol1(); addChild(s1); s1.x=95; s1.y=100; var s2:symbol2=new symbol2(); addChild(s2); s2.x=245; s2.y=100; var s3:symbol3=new symbol3(); addChild(s3); s3.x=395; s3.y=100; var s4:symbol4=new symbol4(); addChild(s4); s4.x=545; s4.y=100; } } }

Obviously it’s a bit unoptimized, just think about if we had a thousand objects. That’s when getDefinitionByName comes into play. It returns a reference to the class object of the class specified by the name parameter.

This means the same script can be written this way:

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package { import flash.display.Sprite; import flash.utils.* public class Main extends Sprite { public function Main() { var symbolName:String; var symbolClass:Class; var s:Sprite; for (var i:int=1; i<=4; i++) { symbolName="symbol"+i; symbolClass=getDefinitionByName(symbolName) as Class; s=new symbolClass(); addChild(s); s.x=95+150*(i-1); s.y=100; } } } }

DisplayObjects names are passed as strings in getDefinitionByName method and created as generic classes that can be used anywhere in the movie [...]