Blog by Jeevan

[1] Singleton When a class is restricted to just one instantiation, that one object is called a singleton. A singleton class returns the same instance no matter how many times an application requests it.   Example : + (instancetype)sharedManager   {      static DocumentManager * sharedDocumentManager = nil;      static dispatch_once_t onceToken;      dispatch_once(&onceToken, ^{          sharedDocumentManager = [[DocumentManager alloc] init];          NSLog(@"Singleton memory address: %@", sharedDocumentManager);      });      return sharedDocumentManager; } [2] Abstract Factory  Provide an interface for creating families of related or dependent objects without specifying their concrete classes. Creates a base class with abstract methods defining methods for the objects that should be created. Each factory class w...