CODEWITHSUNDEEP
actionscript-3flash
Deban
Deban

Reputation: 13

Check if class extends another class

To be clear, I want to check a class, not an instance of that class.

public function changeScene(newScene:Class):void 
{
  if(newScene isExtending Scene)
  //...
}

It's a variable of type Class.

Edit: More details. What the function does (simplified):

public function changeScene(newScene:Class):void 
{
    currentScene.finish(); //Finish the scene that is about to change

    //Check if the new scene don't exist prior this point
    if (!scenes[newScene])  //Look in dictionary
        addScene(newScene); //Create if first time accessing it

    scenes[newScene].caller = currentScene["constructor"];
    currentScene = scenes[newScene];
    currentScene.start();
}

This question doesn't work for me because I don't create new instances all the time, I reused them most of the time. The instances are stored in a dictionary using the class as the key.

Upvotes: 1

Views: 144

Answers (2)

null
null

Reputation: 5255

The other question doesn't work for me because I don't create new instances all the time, I reused them most of the time. The instances are stored in a dictionary using the class as the key.

I beg to differ.

The factory pattern encapsulates the entire creation of the object of a certain class. That also includes limiting how often the class is instantiated. If you only want the factory to ever produce one object, that's possible. It will turn into a Singleton.

Upvotes: 0

BadFeelingAboutThis
BadFeelingAboutThis

Reputation: 14406

Here is the only way I can think of to do this without instantiating objects:

You use flash.utils.getQualifiedSuperclassName the get the super class of a class. Since that returns a string, you have to then use flash.utils.getDefinitionByName to get the actual class reference.

So you could write a function that walks up the inheritance until it either finds a match, or reaches Object (the base of everything).

import flash.utils.getQualifiedSuperclassName;
import flash.utils.getQualifiedClassName;
import flash.utils.getDefinitionByName;

function extendsClass(cls:Class, base:Class):Boolean {
    while(cls != null && cls != Object){
        if(cls == base) return true;
        cls = getDefinitionByName(getQualifiedSuperclassName(cls)) as Class; //move on the next super class
    }
    return false;
}

trace(extendsClass(MovieClip,Sprite)); //true
trace(extendsClass(MovieClip,Stage)); //false

Upvotes: 1

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