Declare conformance to objective-c protocol with a category and implement it with another category

Question

clang reports that Test1(FooBar) doesn't implement foo or bar , despite foo being implemented in Test1(Foo) and bar being implemented in Test1 . Since Test1(Foo) 's @interface exists above Test1(FooBar) 's, clang should see that Test1(Foo) implements foo and shouldn't require me to implement it in Test1(FooBar) . Since Test1 implements bar , clang shouldn't require me to implement it in Test1(FooBar) .

@interface Test1 : NSObject

- (void) bar;

@end

@interface Test1(Foo)

- (void) foo;

@end

@protocol FooBar <NSObject>

- (void) foo;
- (void) bar;

@end

@interface Test1(FooBar)<FooBar>

@end

@implementation Test1(Foo)

- (void) foo {
}

@end

@implementation Test1(FooBar)

@end

Answer 1

My understanding is that this line:

@interface Test1(FooBar)<FooBar>

can be interpreted in plain english as "The category FooBar on class Test1 should implement protocol FooBar". In other words, the protocol applies to the category, not the class.