(Not a really good) use of RACStashSubject

gistfile1.m

- (instancetype)initWithURL:(NSURL *)url type:(NSString *)type {
  self = [super initWithURL:url type:type];
  if (!self) {
    return nil;
  }
  _contentBacking = [RACReplaySubject replaySubjectWithCapacity:1];
  NSError *error;
  NSString *content = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
  if (!error) {
    [_contentBacking sendNext:content];
  } else {
    [_contentBacking sendError:error];
  }
  
  RACStashSubject *unsavedContent = [RACStashSubject stashSubjectWithLatestValueOnly:YES];
  [_contentBacking subscribe:unsavedContent];
  
  @weakify(self);
  
  // Autosave every 3 minutes, with a 1 minute leeway
  // TODO: if the content isn't changed until `unsavedContent` is subscribed to, the next content change will trigger a save. `-[id<RACSubscribable> windowWithStart:close:]` would behave better in that regard
  [[RACSubscribable interval:180.0 withLeeway:60.0] subscribeNext:^(id x) {
    // NOTE: this only works because `+[RACSubscribable interval:withLeeway:]` delivers on the main thread, and we deliver the unsaved content on a non-main thread, so `unsavedContentDisposable` is properly set by the time the `subscribeNext:` block is called
    __block RACDisposable *unsavedContentDisposable = [[unsavedContent deliverOn:fsScheduler()] subscribeNext:^(NSString *x) {
      @strongify(self);
      [self saveContent:x];
      [unsavedContentDisposable dispose];
    }];
  }];
  
  return self;
}