RACSignal創(chuàng)建流程

 //1、創(chuàng)建信號(hào)
    RACSignal * signal = [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {
        //3、發(fā)送信號(hào)
        [subscriber sendNext:@"LGCooci"];
        return nil;
    }];
   
    //2、訂閱信號(hào)
    [signal subscribeNext:^(id  _Nullable x) {
        NSLog(@"訂閱到了%@",x);
    }];

• 創(chuàng)建信號(hào) - createSignal()
• 訂閱信號(hào) - subscribeNext()
• 發(fā)送信號(hào) - sendNext() sendCompleted() sendError()

核心邏輯源碼分析

創(chuàng)建信號(hào)

+ (RACSignal *)createSignal:(RACDisposable * (^)(id<RACSubscriber> subscriber))didSubscribe {
    return [RACDynamicSignal createSignal:didSubscribe];
}

+ (RACSignal *)createSignal:(RACDisposable * (^)(id<RACSubscriber> subscriber))didSubscribe {
    RACDynamicSignal *signal = [[self alloc] init];
    signal->_didSubscribe = [didSubscribe copy];
    return [signal setNameWithFormat:@"+createSignal:"];
}

1. createSignal 帶入一個(gè)block:didSubscribe
2. RACDynamicSignal創(chuàng)建信號(hào)，并保存block：_didSubscribe

訂閱信號(hào)

- (RACDisposable *)subscribeNext:(void (^)(id x))nextBlock {
    NSCParameterAssert(nextBlock != NULL);
    
    RACSubscriber *o = [RACSubscriber subscriberWithNext:nextBlock error:NULL completed:NULL];
    return [self subscribe:o];
}

+ (instancetype)subscriberWithNext:(void (^)(id x))next error:(void (^)(NSError *error))error completed:(void (^)(void))completed {
    RACSubscriber *subscriber = [[self alloc] init];
    subscriber->_next = [next copy];
    subscriber->_error = [error copy];
    subscriber->_completed = [completed copy];
    return subscriber;
}

1. RACSubscriber創(chuàng)建訂閱者o, 傳入block:nextBlock
2. RACSubscriber內(nèi)部保存blcok:nextBlock的_next,_error,_completed
3. 調(diào)用[self subscribe:o],此時(shí)的self即為：RACDynamicSignal對(duì)象

進(jìn)入RACDynamicSignal的subscribe內(nèi)部：

- (RACDisposable *)subscribe:(id<RACSubscriber>)subscriber {
    NSCParameterAssert(subscriber != nil);

    RACCompoundDisposable *disposable = [RACCompoundDisposable compoundDisposable];
    subscriber = [[RACPassthroughSubscriber alloc] initWithSubscriber:subscriber signal:self disposable:disposable];

    if (self.didSubscribe != NULL) {
        RACDisposable *schedulingDisposable = [RACScheduler.subscriptionScheduler schedule:^{
            RACDisposable *innerDisposable = self.didSubscribe(subscriber);
            [disposable addDisposable:innerDisposable];
        }];

        [disposable addDisposable:schedulingDisposable];
    }
    
    return disposable;
}

4. RACPassthroughSubscriber(接受了RACSubscriber協(xié)議)傳入subscriber重新初始化了新的subscriber
5. 調(diào)用self.didSubscribe(subscriber), 這里的didSubscribe即為創(chuàng)建信號(hào)時(shí)候保存的block, 這里就直接就把subscriber回調(diào)了回去

發(fā)送信號(hào)

//3、發(fā)布信號(hào)
[subscriber sendNext:@"LGCooci"];
[subscriber sendCompleted];

- (void)sendNext:(id)value {
    @synchronized (self) {
        void (^nextBlock)(id) = [self.next copy];
        if (nextBlock == nil) return;

        nextBlock(value);
    }
}
- (void)sendError:(NSError *)e {
    @synchronized (self) {
        void (^errorBlock)(NSError *) = [self.error copy];
        [self.disposable dispose];

        if (errorBlock == nil) return;
        errorBlock(e);
    }
}
- (void)sendCompleted {
    @synchronized (self) {
        void (^completedBlock)(void) = [self.completed copy];
        [self.disposable dispose];

        if (completedBlock == nil) return;
        completedBlock();
    }
}

1. 這里的subscriber即為訂閱信號(hào)調(diào)用didSubscribe回調(diào)傳出來的RACPassthroughSubscriber對(duì)象, 當(dāng)調(diào)用sendNext,sendError,sendCompleted的時(shí)候，就會(huì)通過保存的.next, .error, .completed block進(jìn)行回調(diào)，最后就完成了整個(gè)流程