[haxe] Dynamically create instance from a list of classes

[Georges Gabereau]

Hey all,

Not sure this is even possible in Haxe, but here's what I'm trying to do:

class A { }
class B { }
class C { }


class Main {
    private var classes:Array<Dynamic>;
    private var index:Int;
 
    function new(){
        index = 0;
        classes = [A, B, C];
    }

    function nextInstance():Dynamic{
        klass = classes[index];
        return new klass();
    }
}

main=new Main();
main.nextInstance(); # Returns in instance of A
main.nextInstance(); # Returns an instance of B
main.nextInstance(); # Returns an instance of C

Hopefully this example makes sense.

I'm creating a game and each level is a sub-class on my class Level. In the game, I want to have a list of the Level classes and just instantiate the next one once a level is complete. I could just create instances of every level on initial app load, but that seems wasteful and unnecessary.

Thanks!

[Jason O'Neil]

Your list of levels would be defined like this:

var levels:Array<Class<BaseLevelClass>> = [Level1, Level2, Level3];

And then to create them

var level = Type.createInstance(levels[0], []);

With this syntax haxe will know that "level" is of the type
"BaseLevelClass" and will be able to use whatever methods or properties
your BaseLevelClass has.

Hope this helps...

Jason

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[Georges Gabereau]

This works perfectly. 

Coming from a much more dynamic language, I was having a hard time figuring out the types in that definition.

Thanks for the quick reply!

[Jason O'Neil]

No worries, glad I was able to help :)

Good luck with your game!

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[Heinz Hölzer]

You can also create anonymous functions that act as factories for your levels. Then everything is statically typed.

class BaseLevel
class A extends BaseLevel{ }
class B extends BaseLevel{ }
class C extends BaseLevel{ }


class Main {
    private var classes:Array<Void->BaseLevel>;

    private var index:Int;
 
    function new(){
        index = 0;

        classes = [function () return new A(), function () return new B(), function () return new C()];
    }

    function nextInstance():BaseLevel{
        return classes[index]();
    }
}

main=new Main();
main.nextInstance(); # Returns in instance of A
main.nextInstance(); # Returns an instance of B
main.nextInstance(); # Returns an instance of C