Extract protocol

// Dog.h
@interface Dog
// This method will be extracted
// to a protocol
- (void)swim;
- (void)run;
- (void)eat;
@end

// Dog.m
@implementation Dog {
}
- (void)swim {
    NSLog(@"I am swimming");
}
- (void)run {
    NSLog(@"I am running");
}
- (void)eat {
    NSLog(@"I am eating");
}
@end

// New protocol
// Swimmable.h
@protocol Swimmable <NSObject>>
- (void)swim;
@end

// Dog.h
@interface Dog <Swimmable>
- (void)run;
- (void)eat;
@end

// Dog.m
@implementation Dog {
}
- (void)swim {
    NSLog(@"I am swimming");
}
- (void)run {
    NSLog(@"I am running");
}
- (void)eat {
    NSLog(@"I am eating");
}
@end