PBMainThreadSynchronousScheduler

PBMainThreadSynchronousScheduler.h

#import <ReactiveCocoa/RACQueueScheduler+Subclass.h>

/**
 * This scheduler class schedules values sent down a signal on the main thread synchronously 
 * if they're sent on the main thread as opposed to RACScheduler.mainThreadScheduler 
 * which always sends values asynchronously.
 */
@interface PBMainThreadSynchronousScheduler : RACQueueScheduler

+ (instancetype)mainThreadSynchronousScheduler;

@end

PBMainThreadSynchronousScheduler.m

@implementation PBMainThreadSynchronousScheduler

+ (instancetype)mainThreadSynchronousScheduler {
  static dispatch_once_t onceToken;
  static PBMainThreadSynchronousScheduler *mainThreadSynchronousScheduler;
  dispatch_once(&onceToken, ^{
    mainThreadSynchronousScheduler = [[PBMainThreadSynchronousScheduler alloc] initWithName:@"com.getpebble.ios.RACScheduler.mainThreadSynchronousScheduler" queue:dispatch_get_main_queue()];
  });
  
  return mainThreadSynchronousScheduler;
}

- (RACDisposable *)schedule:(void (^)(void))block {
  NSCParameterAssert(block != NULL);
  
  RACDisposable *disposable = [[RACDisposable alloc] init];
  
  dispatch_block_t performBlock = ^{
    if (!disposable.disposed) {
      [self performAsCurrentScheduler:block];
    }
  };
  
  if ([NSThread isMainThread]) {
    performBlock();
  }
  else {
    dispatch_async(self.queue, performBlock);
  }
  
  return disposable;
}

@end