How to cast with class in variable?

[Théo Sabattié]

Hi All'

We can do :

cast(myInstance, MyClass);

But I want define MyClass as paramater of function or in a variable.

var lClass:Class<Dynamic> = MyClass;

cast(myInstance, lClass);

That does not work:

src/Main.hx:20: characters 27-28 : Unexpected )

Any idea?

[Théo Sabattié]

It is for pixijs, I want to add a getter which return the researched child using generic type

    private function getChild<T>(childName:String):T {

        var child:DisplayObject = getChildByName(childName);

        

        if (child == null) {

           throw "Child with name " + childName + " not found";

        }

        

        if (!Std.is(child, T)) {

            throw "Child with name " + childName + " is not an instance of " + Type.getClassName(T);

        }

        

        return cast(child, T);

    }

I have those errors:

src/UIComponent.hx:79: characters 22-23 : Type parameter T is only available at compilation and is not a runtime value

src/UIComponent.hx:85: characters 27-28 : Type parameter T is only available at compilation and is not a runtime value

src/UIComponent.hx:86: characters 97-98 : Type parameter T is only available at compilation and is not a runtime value

src/UIComponent.hx:89: characters 15-29 : Can't cast to a type parameter

src/UIComponent.hx:76: lines 76-90 : Missing return getChild.T

Build halted with errors (haxe.exe).

How can I do test and cast?

[clemos]

I think you can just `return cast child;`, which the compiler will
infer to whatever T is.

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[Théo Sabattié]

I can do that but I have to check if displayObject is an instance of T.

And 

Std.is(child, T)

generate:

src/UIComponent.hx:79: characters 22-23 : Type parameter T is only available
> at compilation and is not a runtime value

[clemos]

Yeah you can't do that, you have to pass the actual class at runtime,
something like:
private function getChild<T>(childName:String, type: Class<T>): T {
//...
if( !Std.is( child, type ) {
//...
}
//...
}

On Tue, May 31, 2016 at 10:50 AM, Théo Sabattié

[Théo Sabattié]

Great! It's running! :)

Thanks clemos.

I thought use 

getChild<Graphics>("_gridZone", Graphics);

But it is running with

getChild("_gridZone", Graphics);

I have juste a last problem:

private function getChild<T>(childName:String, type:Class<T>):T {

        var child:DisplayObject = getChildByName(childName);

        

        if (child == null) {

           throw "Child with name " + childName + " not found";

        }

        

        if (!Std.is(child, type)) {

            throw "Child with name " + childName + " is not an instance of " + Type.getClassName(type);

        }

        

        return cast child;

    }

Type.getClassName(type)

return null

I can't inform user.

untyped type.prototype.constructor.name

return "i"