Template for a Shared Instance (Singleton) in Objective-C

Header.h

+ (NSObject*)sharedInstance;

Implementation.m

+ (NSObject*)sharedInstance
{
   static NSObject* sharedInstance_;
   
   @synchronized( self )
   {
      if( !sharedInstance_ )
      {
         sharedInstance_ = [[NSObject alloc] init];
      }
      
      return sharedInstance_;
   }
}