Inheritance problem with .super()

By Nakor | Jan 9, 2009

I’m having a problem and I’m not quite sure what is going on. I’ll admit to being relatively new to AS3, but I’m a fairly competent programmer in several OO programming languages as well as AS2.

Here is my problem. I have two MovieClips in my library, which are virtually identical except in colour. Each has two MovieClips inside them, one a static graphic, the other having nine frames, each one with a number from 1-9 one it. These have the instance names of CoinNumber_mc and sCoinNumber_mc. These MovieClips are linked to the classes Coin and SpecialCoin respectively, and SpecialCoin extends Coin.

I then have a third class which creates a grid of Coins and replaces some of these with SpecialCoins.

Now heres my problem. In the constructors for the two coin classes they set a value proprety to a random number between 1-9 and goes to that frame in either CoinNumber_mc or sCoinNumber_mc. However when I run it I get this error:

Code:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

        at Coin$iinit()

        at SpecialCoin$iinit()

        at SphereBreak/::addSpecialCoins()

        at SphereBreak/::setUpGrid()

        at SphereBreak$iinit()

        at spherebreak_fla::MainTimeline/spherebreak_fla::frame1()

Now if I’m reading this stacktrace correctly, when the SpecialCoin constructor is being called, its calling it’s super constructor and when it tries to make CoinNumber go to the a frame and can’t find it, it throws an exception.

Here’s my constructors:

ActionScript Code:


public function Coin()
{
    delay = 0;
    pressed = false;
    value = Math.ceil(Math.random()*MAX_VALUE);
    this.CoinNumber_mc.gotoAndStop(value);
}

ActionScript Code:


public function SpecialCoin()
{
             value = Math.ceil(Math.random()*MAX_VALUE);
    this.sCoinNumber_mc.gotoAndStop(value);
    pressed = false;
}