ActionScript-3中的Minusassign（-=）语法错误

Question

Why can't I compile this little piece of code ?
I'm overriding x and y in my class so that's why I need super.x .

public class SimpleSprite extends Sprite
{
    override public function set x(value: Number): void
    {
        super.x -= 12;
        //super.x = super.x - 12;
    }
}

// or
public class SimpleSprite2 extends Sprite
{
    public function get xx(): Number
    {
        return super.x;
    }

    public function set xx(value: Number): void
    {
        super.x = value;
    }

    public function SimpleSprite2()
    {
        xx -= 12;
        super.x -= 12;
        // Error: Syntax error: expecting semicolon before minusassign.
    }
}

I know I can write super.x = super.x - 12; but im lazy and i dont want 2 look 4 these inconsistencies when i get hit by syntax errors im also very much accustomed to those shortcuts with -=

---

Looks like my IDE (FlashDevelop 4.2.3) bears the blame for this.

Answer 1

There's nothing syntactically wrong with what your doing. Your code works fine in my Flash Builder 4.7.

However, remember that instance.x -= value; is short for

instance.x = instance.x - value; 
//ie. 
instance.[set]x = instance.[get]x - value;

I mention this because of your top code:

override public function set x(value: Number): void
{
    super.x -= 12;
    //super.x = super.x - 12;
}

Makes me think you're trying to do something funny. Why are you decrementing in the set function?

If you need to have a seperate x value for a subclass, but can't change the interface (ie. you still want users to be able to say mySubClassInstance.x = 123.0; ) do this:

public class DerivedSprite extends Sprite
{
    protected var derivedX:Number;
    public override function get x():Number
    {
        super.x = derivedX;
        return derivedX;
    }

    public override function set x(value:Number):void
    {
        super.x = value;
        derivedX = value;
    }

    public function DerivedSprite()
    {
        super();
        derivedX = super.x;
    }
}