[[[DTObservable alloc] init:^(DTSubscriber *subscriber) {

    // Setup some data
    NSDictionary *value = @{@"4": @20};

    // Lets pretend something cpu intensive happens here
    [NSThread sleepForTimeInterval:1.f];

    // Notify the subscriber
    [subscriber next:value];
    [subscriber complete];

}] subscribe:[[DTSubscriber alloc] init:^(NSDictionary *value) {

    // Confirm the result
    BOOL fourTwenty = [value[@"4"] intValue] == 20;

    // Success!
    NSLog(@"Does 4 == 20? %@", fourTwenty ? @"YES" : @"NO");

} onError:^(NSError *error) {
    NSLog(@"%@", error);
}]];