ReactiveCocoa RACSubject Example

gistfile1.m

self.gestureRecognizerIsRunningSubject = [RACSubject subject];
self.gestureRecognizerValueSubject = [RACSubject subject];

RAC(self.someView.frame) = [self.gestureRecognizerValueSubject map:^id(NSValue *value) {
   CGPoint location = [value CGPointValue];

   CGFloat size = 100.0f;

   return [NSValue valueWithCGRect:CGRectMake(location.x - size/2.0f, location.y - size/2.0f, size, size)];
}];