Proper Objective-C Helper “Wannabe” Private methods?

Question

While I hate to beat a horse to death on this subject (I\'ve read through various articles about this), but would just like to get more opinions on this matter before I create m

Answer 1

If you just need a reusable set of code that absolutely cannot be overridden by a subclass, you could just make a regular C function instead of a method. If the function is declared within the scope of the class @implementation block, it can still get access to all the private ivars of the object. You'd need to pass in a pointer to self, though, since a function isn't bound to a particular object

So it would look like this:

static BOOL isInValidState(MyClass *);

@implementation MyClass

static BOOL isInValidState(MyClass *self) {
    if (self->somePrivateIvar == nil) {
        return NO;
    }

    if ([self->someString isEqualToString:@"pigsAreFlying"]) {
        return NO;
    }

    return YES;
}

- (void)method1 {
    if (isInValidState(self) == NO) {
        return;
    }
    // Do whatever method 1 does
}

- (void)method2 {
    if (isInValidState(self) == NO) {
        return;
    }
    // Do whatever method 2 does
}

@end

Since functions are not part of the method list of a class, this error checking method cannot ever be overridden. Since we declared it static, it is only accessible within the scope of this file, which means that it's effectively private; it cannot be called by an object of any other class.