RAC的doNext副作用

副作用的操作——doNext：

// 副作用的操作doNext：后期需要深入的理解
RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
  [subscriber sendNext:@1];
  [subscriber sendNext:@2];
  [subscriber sendNext:@4];
  [subscriber sendCompleted];
  return [RACDisposable disposableWithBlock:^{
    NSLog(@"完成");
  }];
}];

RACSignal *signalB = [signalA doNext:^(id x) {
  NSLog(@"doNext:%@",x);
}];   

[[signalB subscribeNext:^(id x) {
  NSLog(@"subscribeNext:%@",x);
}] dispose];

2021-04-15 11:30:46.809094+0800 xxxxxx[3504:1044105] doNext:1

2021-04-15 11:30:46.809133+0800 xxxxxx[3504:1044105] subscribeNext:1

2021-04-15 11:30:46.809143+0800 xxxxxx[3504:1044105] doNext:2

2021-04-15 11:30:46.809152+0800 xxxxxx[3504:1044105] subscribeNext:2

2021-04-15 11:30:46.809161+0800 xxxxxx[3504:1044105] doNext:4

2021-04-15 11:30:46.809169+0800 xxxxxx[3504:1044105] subscribeNext:4

2021-04-15 11:30:46.810342+0800 xxxxxx[3504:1044105] 完成