Trouble with error

Question

In an attempt to eliminate unnecessary classes I am trying to
combine 2 of them but no having much luck this is the error I am
getting:
TypeError: Error #1009: Cannot access a property or method of
a null object reference.
at OButton/initializeMenu()
at OButton()
at flash.display::Sprite/constructChildren()
at flash.display::Sprite()
at flash.display::MovieClip()
at ASMain()

Answer 1

Well, as it turns out I'm probably not the teaching type!
David Stiller, where are you! :-)
Ok, let's attempt to explain what you are doing here. My
reference is the example we discussed in the other thread so keep
that in mind.
In the example you have a button as a movieclip in the
library and linked that to a class - in the example the class is
called CategoryButton.as. The combination of that visual asset in
the library and the class defines ONE object. Think of it this way:
we could have used the drawing API's in the class to define the
visual aspects of the button, in which case we would just have a
class that makes up our button as a whole. Having a asset in the
library and linking that to a class is basically the same thing. In
the end you have ONE object.
So, let's look at that 'object' thing a bit more, a real life
comparison: the engine in your car is an object, but the parts that
make up the engine are also objects. Because every object in the
engine has certain properties the thing in the end does the job we
expect it to do. When the engine doesn't start, obviously something
is wrong and we need the car doctor. He/she analyzes the problem,
takes out a part (one of the objects in the system), fiddles with a
screwdriver and a piece of cloth, puts the part back in and there
you go again, happily polluting the air while you're at it. Now you
have to know, in the beginning the engine only had a few parts. But
it was hard to repair! So they decided to split up the system in
several subsystems and the subsystems in parts. Now it became very
easy to repair the thing. Back to programming. What do you know?
It's the same stuff all over again! We actually learned something
from history. In the beginning we wrote zillions of lines of code
in just one file. Then ancenstors of the famous engine builders
decided that they could do the same thing here! Smart guys... So
what exactly is there to learn here. Well, it's probably better to
have more classes than trying to cut down on classes. It's just
easier to repair something when you can isolate the problem to one
tiny part in the system!
Now looking at your class, here is what you are doing: you
create a part of the engine and are trying to stuff 5 of the exact
same parts in there! Highly creative and probably something that
David Copperfield could do but you are Big Mama In The Mud!
The buttons are individual parts that together (as a
collection) make up a subsytem, called Menu. The Menu is the casing
of the parts and we attach some wires to it to communicate with
other subsystems. The buttons are 'switches'. In the example, when
they are clicked they can switch themselves off but they just don't
know when to switch to 'on' again. That is where the Menu comes in.
It receives a signal from one of its parts so it can decide to
switch a button on again.
Good luck and now I'm gone because my copy of Flash CS4 has
downloaded!