RAC笔记（1）-- RACMulticastConnectio

RACMulticastConnection

- (void)mutlticastConnect {
    RACSignal *signal = [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {//subscriber：RACSubject->RACPassthroughSubscriber
        NSLog(@"发送请求");
        [subscriber sendNext:@"发送数据"];
        return nil;
    }];
    RACMulticastConnection *connect = [signal publish];
    [connect.signal subscribeNext:^(id  _Nullable x) {//connect->_signal: <RACSubject
        NSLog(@"11:%@", x);
    }];
    [connect.signal subscribeNext:^(id  _Nullable x) {
        NSLog(@"22:%@", x);
    }];
    [connect.signal subscribeNext:^(id  _Nullable x) {
        NSLog(@"33:%@", x);
    }];
    [connect connect];//执行signal的block：connect.sourceSignal.didSubscribe(connect.subject)
    [connect.signal subscribeNext:^(id  _Nullable x) {
        NSLog(@"44:%@", x);
    }];
    [connect connect];
    [connect.signal subscribeNext:^(id  _Nullable x) {
        NSLog(@"55:%@", x);
    }];
}

///打印
2020-04-23 18:22:15.932457+0800 RacDemo[1626:631230] 发送请求
2020-04-23 18:22:15.932587+0800 RacDemo[1626:631230] 11:发送数据
2020-04-23 18:22:15.932632+0800 RacDemo[1626:631230] 22:发送数据
2020-04-23 18:22:15.932670+0800 RacDemo[1626:631230] 33:发送数据

1. 创建原始信号，保存block：didSubscribe

RACSignal *signal = [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {
}];

image.png

2. 创建RACMulticastConnection：connect
   由RACSignal对象signal调用publish得到

RACMulticastConnection *connect = [signal publish];

publish方法：

• 将原始信号signal赋值给_sourceSignal：_sourceSignal = source;
• 创建RACSubject对象赋值给_signal：_signal = subject;

publish方法

- (instancetype)initWithSourceSignal:(RACSignal *)source subject:(RACSubject *)subject {
    NSCParameterAssert(source != nil);
    NSCParameterAssert(subject != nil);

    self = [super init];

    _sourceSignal = source;
    _serialDisposable = [[RACSerialDisposable alloc] init];
    _signal = subject;
    
    return self;
}

3. connect.signal即connect. subject调用订阅方法subscribeNext

[connect.signal subscribeNext:^(id  _Nullable x) {//connect->_signal: <RACSubject
     NSLog(@"11:%@", x);
}];

将订阅者RACSubscriber封装成RACPassthroughSubscriber类型，保存到订阅者subscribers数组

subscribeNext RACSubject.subscribe

4. [connect connect]

原始信号signal订阅subject

[connect connect]

将subject包装成RACPassthroughSubscriber，做为参数发给原始信号signal的block：didSubscribe

RACDynamicSignal.subscribe

执行block：didSubscribe(RACPassthroughSubscriber)

didSubscribe(RACPassthroughSubscriber)

5. RACPassthroughSubscriber的sendNext

[subscriber sendNext:@"发送数据"];

RACPassthroughSubscriber.sendNext

RACPassthroughSubscriber.innerSubscriber是RACSubject类型，来到RACSubject.sendNext，遍历保存的订阅者数组subscribers，发送数据

RACSubject.sendNext

6. connect之后的订阅不会执行

打印 connect

OSAtomicCompareAndSwap32Barrier拿_hasConnected 和 1比较：

• _hasConnected != 1：返回YES且_hasConnected = 1
• _hasConnected == 1：返回NO

connect之后的订阅不会执行block：didSubscribe，所以后面的44、55不打印