Question

I have been doing some reading and a little bit confused, let me explain.

My situation:

ClassA.h has some arrays, and ClassA.m has some methods that uses these arrays. I also have ClassB, ClassC, ClassD… that have their own arrays, and their own methods that use these arrays. Up until now I have just been copying and pasting the code into each class.

What I want to do:

I did some reading and found that I want to create a parent class, where all the methods are housed, and then use these methods in my classes:

//parentClass.m
@implementation parentClass

+ (void)commonMethod:(id)sender{

...

}

@end


//classA.m

@implementation classA

- (void)someMethod{
    [parentsClass commonMethod];
}

@end


//classB.m

@implementation classB

- (void)someMethod{
    [parentClass commonMethod];
}

@end

The Problem:

So I moved the methods to the parentClass.m, and the arrays to the parentClass.h. My problem is when I try to build and run, I get errors like Instance variable <someArray> accessed in class method. I am not sure what to do. Is the only way around this problem to declare my arrays above the @interface in the .h file?

---

EDIT: The reason I want to use this technique for using methods in the parent class is because I would like to call the methods like this:

[commonClass commonMethod];

And not have to declare an instance of the parent class every time.

THANKS!

Answer 1

Regardless of inheritance, you have to use instance methods (and not class methods) if you want to access instance variables, like your array. An instance method is indicated by a - (minus) before the method signature, while class methods use a +.