Extract superclass

// All methods of the Dog class
// will be moved to a superclass
// Dog.h
@interface Dog : NSObject
- (void)run;
- (void)eat;
@end
 // Dog.m
  @implementation Dog {
}
-(void)run {
    NSLog(@"I am running");
}
- (void)eat {
    NSLog(@"I am eating");
}
@end

// New superclass
// Animal.h
@interface Animal : NSObject
- (void)run;
- (void)eat;
@end
 // Animal.m
  @implementation Animal {
}
-(void)run {
    NSLog(@"I am running");
}
- (void)eat {
    NSLog(@"I am eating");
}
@end

// The Dog class is now a subclass
// of the Animal class
// Dog.h
@interface Dog : Animal
@end
// Dog.m
@implementation Dog {
}
@end