typedef NS_ENUM (NSUInteger,PostType){
    PostTypeVideo,
    PostTypePhoto,
    PostTypePlain,
};
@interface Post:NSObject
@property (copy) NSString *title;
@property NSDate  *createdDate;
// helper for creating Post Object
+ (Post*) postWithType:(PostType)type;
-  (void) animatePost;
@end
@implementation Post
+(Post*)postWithType:(PostType)type{
    switch(type){
        case PostTypeVideo :
                return [PostVideo new];
                break;
        case PostTypePhoto :
                return  [PostPhoto new];
                break;
        case  PostTypePlain:
                return  [PostPlain new];
                break;
    }
}
-(void) animatePost{
    // Subclasses implements this
}
@end
@interface PostVideo : Post
@end
@implementation PostVideo
- (void)animatePost{
    NSLog(“This is an video Animation Code!!!!")
}
@end