RACSignal+continueInBackground.m

- (RACSignal*) continueInBackground
{
    return [[RACSignal createSignal:^(id<RACSubscriber> subscriber) {
        UIApplication* app = UIApplication.sharedApplication;

        __block UIBackgroundTaskIdentifier taskID;
        RACCompoundDisposable* compoundDisposable = [RACCompoundDisposable compoundDisposable];
        RACDisposable* backgroundTaskDisposable = [RACDisposable disposableWithBlock:^{
            [app endBackgroundTask:taskID];
        }];

        // To ensure the background task isn't ended before the error or completed event
        // is delivered we have to remove the background disposable from our compound
        // disposable. Otherwise, the internal signal executes the disposable before actually
        // invoking the error or completion blocks. As such, we have to do this dance with
        // the background disposable.

        taskID = [app beginBackgroundTaskWithExpirationHandler:^{
            NSLog(@"Background task timed out.");
            [compoundDisposable removeDisposable:backgroundTaskDisposable];
            [subscriber sendError:[NSError errorWithDomain:RACSignalErrorDomain code:RACSignalErrorTimedOut userInfo:nil]];
            [backgroundTaskDisposable dispose];
        }];

        RACDisposable* subscriptionDisposable = [self subscribeNext:^(id x) {
            [subscriber sendNext:x];
        } error:^(NSError *error) {
            [compoundDisposable removeDisposable:backgroundTaskDisposable];
            [subscriber sendError:error];
            [backgroundTaskDisposable dispose];
        } completed:^{
            [compoundDisposable removeDisposable:backgroundTaskDisposable];
            [subscriber sendCompleted];
            [backgroundTaskDisposable dispose];
        }];

        // Add the background disposable last since it should run after the subscription
        // is cleaned up.
        [compoundDisposable addDisposable:subscriptionDisposable];
        [compoundDisposable addDisposable:backgroundTaskDisposable];
        return compoundDisposable;
    }]
    setNameWithFormat:@"[%@] -continueInBackground", self.name];
}