What's the correct method to subclass a singleton class in Objective -C?

Question

I have created a singleton class and I want to create a class which is subclass of this singleton class, what is the correct method to do it

Answer 1

I had the same problem. This is how to solve: You need to use a static dictionary to subclass a singleton. For exemple:

Class A : NSObject -> Singleton

Class B : A

Class C : A

@implementation A

// Dictionary that holds all instances of API subclasses
static NSMutableDictionary *_sharedInstances = nil;

+ (instancetype)sharedInstance
{
    id sharedInstance = nil;
    @synchronized(self)
    {
       NSString *instanceClass = NSStringFromClass(self);

       if (_sharedInstances == nil)
           _sharedInstances = [NSMutableDictionary dictionary];

       // Looking for existing instance
       sharedInstance = [_sharedInstances objectForKey:instanceClass];

       // If there's no instance – create one and add it to the dictionary
       if (sharedInstance == nil) 
       {
          sharedInstance = [[super allocWithZone:nil] init];
          [_sharedInstances setObject:sharedInstance forKey:instanceClass];
       }
   }
   return sharedInstance;

}

Now you can use [B sharedInstance] and [C sharedInstance] without problems!