RAC merge

    RACSignal *nameSignal = RACObserve(self, name);
    RACSignal *messageSignal = RACObserve(self, message);
    [[nameSignal merge:messageSignal] subscribeNext:^(id  _Nullable x) {
        NSLog(@"%@", x);
    }];

输出
2018-06-05 18:03:49.019963+0800 racTest[17382:7469000] (null)
2018-06-05 18:03:49.020771+0800 racTest[17382:7469000] (null)

    RACSignal *nameSignal = RACObserve(self, name);
    RACSignal *messageSignal = RACObserve(self, message);
    [[nameSignal merge:messageSignal] subscribeNext:^(id  _Nullable x) {
       
        NSLog(@"%@", x);
    }];
    
    self.name = @"zhangsan";
    self.name = @"zhangsan";
    self.message = @"lisi";

输出
2018-06-05 18:03:49.019963+0800 racTest[17382:7469000] (null)
2018-06-05 18:03:49.020771+0800 racTest[17382:7469000] (null)
2018-06-05 18:03:49.021173+0800 racTest[17382:7469000] zhangsan
2018-06-05 18:03:49.021430+0800 racTest[17382:7469000] zhangsan
2018-06-05 18:03:49.021644+0800 racTest[17382:7469000] lisi