KittenYang

void Swizzle(Class c, SEL orig, SEL new) {  
  Method origMethod = class_getInstanceMethod(c, orig);
  Method newMethod = class_getInstanceMethod(c, new);
  if (class_addMethod(c, orig, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))){
    class_replaceMethod(c, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
  } else {
    method_exchangeImplementations(origMethod, newMethod);
  }
}

KittenYang

static const int target_key;  
@implementation UIGestureRecognizer (Block)

+(instancetype)nvm_gestureRecognizerWithActionBlock:(NVMGestureBlock)block {
  return [[self alloc]initWithActionBlock:block];
}

- (instancetype)initWithActionBlock:(NVMGestureBlock)block {
  self = [self init];
  [self addActionBlock:block];