RACwaterfallDemo

RACwaterfall.m

// Define function 
- (RACSignal *)RACSignalDemoA {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSLog(@"handle A");
        [subscriber sendNext:@"A"];
        [subscriber sendCompleted];
        return nil;
    }];
}

- (RACSignal *)RACSignalDemoB {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSLog(@"handle B");
        [subscriber sendNext:@"B"];
        [subscriber sendCompleted];
        return nil;
    }];
}

- (RACSignal *)RACSignalDemoC {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSLog(@"handle C");
        [subscriber sendNext:@"C"];
        [subscriber sendCompleted];
        return nil;
    }];
}

// demo
[[[[[self RACSignalDemoA] doNext:^(id  _Nullable x) {
    NSLog(@"function : %@", x);

}] then:^RACSignal * _Nonnull{
    return [[self RACSignalDemoB] doNext:^(id  _Nullable x) {
        NSLog(@"function : %@", x);
    }];

}] then:^RACSignal * _Nonnull{
    return [[self RACSignalDemoC] doNext:^(id  _Nullable x) {
        NSLog(@"function : %@", x);
    }];

}] subscribeNext:^(id  _Nullable x) {
    NSLog(@"function : %@", x);

} error:^(NSError * _Nullable error) {
    NSLog(@"function error");

} completed:^{
    NSLog(@"complete");
}];

// output
/*
handle A
function : A
handle B
function : B
handle C
function : C
function : C
complete
*/