What can I do if two methods call each other and I don't want to make one of them public in the header file?

Question

I have two methods -a and -b. -a calls sometimes -b, and -b sometimes calls -a. Both methods are intended to be private, and not called from outside.

But I had to make one of them public in the .h file, because otherwise the compiler would go crazy and give a warning for either one of them.

Is there any valid and good-practise solution for that problem?

Answer 1

Implement a protocol.

or

Write a second header file with a category.

Answer 2

Traditionally, what you'd do is define a category (something like @interface MyClass (MyClass_Private) inside the implementation file that declares the private methods. Apple recently introduced a feature called a class extension that is intended for this exact case. It's basically a specialization of a category, but the class has to implement the methods when it's first defined. It looks like:

@interface MyObject ()
    - (void)setNumber:(NSNumber *)newNumber;
@end

Answer 3

If you really want the functions to be private, you need to declare them as static. To eliminate the cyclic dependency, one should be declared before the other is defined. Here's a simple example:

static void b(); /* forward declaration */

static void a()
{
    if (foo)
        b(); /* forward-declared, so we're ok */
}

static void b()
{
    if (bar)
        a(); /* already defined, so we're ok */
}

This is all valid C, and so based on the OP's comment I assume this is valid ObjC as well.