RACSignal信号的订阅与发送

RACSignal

订阅信号

订阅信号动作 就是创建一个遵循<RACSubscriber>代理的对象 该对象将接受到信号时要做的动作block保存起来

RACSignal subscribeNext:(void (^)(id x))nextBlock error:(void (^)(NSError *error))errorBlock completed:(void (^)(void))completedBlock {
    
    RACSubscriber *subscriber = [[self alloc] init];
    subscriber->_next = [next copy];
    subscriber->_error = [error copy]    
    subscriber->_completed = [completed copy];
    
    [self subscribe:subscriber];
    
}

具体订阅该信号要做的事情 因为不同子类的信号发送事件不同 需要被子类重写

RACSignal subscribe:(id<RACSubscriber>)subscriber {
    //被子类重写
}

RACSubscriber

遵循RACSubscriber代理 即可发送信号值

- (void)sendNext:(id)value {
    self.nextBlock(value);
}
- (void)sendError:(NSError *)e{
    self.errorBlock(e);
}
- (void)sendCompleted {
    self.completedBlock();
}

发送信号值 即执行保存的执行事件block

RACDynamicSignal

DynamicSignal 即在创建信号时要发送的的信号值已经设定 而在重写subscribe方法时只需要将其发送的值与 next、error、completed block进行匹配执行即可

创建信号

DynamicSignal创建信号 创建时已经包含了信号已经要发送的值
将id<RACSubscriber>信号发送者要发送的值的事件block 存起来，存到signal的_didSubscribeblock属性中

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

订阅信号

订阅信号 即 执行创建信号时保存起来的didSubscribe block send创建信号时发送的值

RACDynamicSignal subscribe:(id<RACSubscriber>)subscriber  {
    self.didSubscribe(subscriber);
}

RASSubject < RACSubscriber >: RACSignal

Subject维持一个数组保存所有需要sendEvent的Subscriber,当需要发送

订阅信号

因为继承自RACSignal 需要重写subscribe:方法

RASSubject )subscribe:(id<RACSubscriber>)subscriber {
    [self.subscribers addObject:subscriber];
}

发送信号

发送信号值 即 遍历数组中的Subcriber 依次send 然后执行subscriber 中保存的nextBlock事件block

- (void)sendNext:(id)value {
    [self enumerateSubscribersUsingBlock:^(id<RACSubscriber> subscriber) {
        [subscriber sendNext:value];
    }];
}

RACBehaviorSubject && RACReplaySubject

RACBehaviorSubject

在内部的currentValue属性会保存上次发送的值 这样在订阅该信号时即能收到最后发送的信号值，进行初始化

+ (instancetype)behaviorSubjectWithDefaultValue:(id)value {
    RACBehaviorSubject *subject = [self subject];
    subject.currentValue = value;
    return subject;
}

发送信号

在发送信号时 保存信号作为最后发送的信号

- (void)sendNext:(id)value {
    self.currentValue = value;
    [super sendNext:value];
}

订阅信号

重写subscribe方法 在每次订阅信号时 发送当前保存的值即最后发送的信号

RACBehaviorSubject  subscribe:(id<RACSubscriber>)subscriber {
    [super subscribe:subscriber];
       [subscriber sendNext:self.currentValue];
}

RACReplaySubject

@property (nonatomic, strong, readonly) NSMutableArray *valuesReceived;

内部有个数组保存了一定量发送过的信号 默认为RACReplaySubjectUnlimitedCapacity（NSUIntegerMax），即保存所有已经发送过的信号，也可以通过initWithCapacity初始化，制动保存多少个已经发送过的信号

- (instancetype)initWithCapacity:(NSUInteger)capacity {
    self = [super init];
    
    _capacity = capacity;
    _valuesReceived = (capacity == RACReplaySubjectUnlimitedCapacity ? [NSMutableArray array] : [NSMutableArray arrayWithCapacity:capacity]);
    
    return self;
}