How to avoid "incomplete implementation" warning in partial base class

coding-style, objective-c, oop

Solution

You could conceivably do something like this:

@implementation Base

- (void)bar
{
    if ([self class] == [Base class]) {
        [self doesNotRecognizeSelector:_cmd];
    }
}

@end

That way, you have an implementation, but by default it raises an exception. However, if a derived class accidentally calls `[super bar]` or does not override `bar`, then the exception won't be raised. If that's not what you want, you could just shorten it to:

@implementation Base

- (void)bar
{
    [self doesNotRecognizeSelector:_cmd];
}

@end

In which case, an exception will be raised, even if a subclass calls `[super bar]` or does not override `bar`.

Problem

I have created a protocol that my classes need to implement, and then factored out some common functionality into a base class, so I did this: ``` @protocol MyProtocol - (void) foo; - (void) bar; @end @interface Base <MyProtocol> @end @interface Derived_1 : Base @end @interface Derived_2 : Base @end @implementation Base - (void) foo{ //something foo } @end @implementation Derived_1 - (void) bar{ //something bar 1 } @end @implementation Derived_2 - (void) bar{ //something bar 2 } @end ``` In this way in my code I use a generic id<MyProtocol>. The code works (as long as Base is not used directly) but the compiler chokes at the end of the implementation of Base with a warning: ``` Incomplete implementation of class Base ``` Is there a way to avoid this warning or, even better, a more proper way to obtain this partially implemented abstract base class behavior in Objc?

Original source

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