Question

I’m aware that Objective-C doesn’t support real private methods. What I’m currently doing to declare ‘private’ methods is adding the following to class .m files:

@interface MyClass() 

- (void) privateMethodName;

@end

The Problem:

If I now add a subclass, and want to use this ‘private’ method, I can’t! I get the error:

Receiver type ‘SubClassName’ for instance message does not declare a
method with selector ‘privateMethodName’

So, if I don’t want non-subclasses to be able to access this method, but do want subclasses to be able to, what can I do? What is the best/proper way of achieving my goal?

Answer 1

You could separate the “protected” interface from the public one. In the primary header, just declare the public methods:

MyMagicThingy.h:

@interface MyMagicThingy: NSObject

- (void) publicMethod;

@end 

Then, have an additional header with protected methods:

MyMagicThingy+Protected.h:

#import "MyMagicThingy.h"

@interface MyMagicThingy (Protected)

- (void) protectedMethods;

@end

You cannot have “real” private/protected/public methods in Objective C (as in: the compiler will enforce access rules. All methods are public). You have to go with a convention.