text: //
  //  SingletonGCD.h
  // From Github From 2010 WWDC video
  
  #import <Foundation/Foundation.h>
  
  #ifndef SYNTHESIZE_SINGLETON_FOR_CLASS
  #define SYNTHESIZE_SINGLETON_FOR_CLASS(classname)                        \
  \
  __strong static classname * shared##classname = nil;    \
  + (classname *)shared##classname {                      \
  \
  static dispatch_once_t pred;                            \
  dispatch_once( &pred, ^{                                \
  shared##classname = [[self alloc] init]; });            \
  return shared##classname;                               \
  }
  #endif
  