RACSignal

RACSignal继承自RACStream，对该抽象类的方法进行了重写实现

`return`方法

+ (RACSignal *)return:(id)value {
    return [RACReturnSignal return:value];
}
/**
RACReturnSignal *signal = [[self alloc] init];
signal->_value = value;
*/

`-bind`方法


/**
实现过程
1. 订阅原始信号值
2. 当原信号发送值时，使用bindblock对其进行转换
3. 如果bindblock返回一个信号，订阅该信号，并在收到该信号值时，将所有值传递给接收者subscriber
4. 如果bindblock请求终止就向原信号发出`-sendError:`消息
5. 当所有信号完成，向订阅者发送`-sendCompleted`
6. 无论何时 当信号发生错误，向订阅者发送-sendError: 消息
*/

- (RACSignal *)bind:(RACSignalBindBlock (^)(void))block

-bind方法在原始信号每次发出消息时，执行RACSignalBindBlock对其进行变换生成一个新的信号

示例:

//示例1：
RACSignal *signal = [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {
    [subscriber sendNext:@1];
    [subscriber sendNext:@2];
    [subscriber sendNext:@3];
    [subscriber sendNext:@4];
    [subscriber sendCompleted];
    return nil;
}];
RACSignal *bindSignal = [signal bind:^RACSignalBindBlock _Nonnull{
    return ^(NSNumber *value, BOOL *stop) {
        //简单的利用bind将 原始信号的值进行了一个变换
        value = @(value.integerValue * value.integerValue);
        return [RACSignal return:value];
    };
}];
[signal subscribeNext:^(id  _Nullable x) {
    NSLog(@"signal: %@", x);
}];
[bindSignal subscribeNext:^(id  _Nullable x) {
    NSLog(@"bindSignal: %@", x);
}];

-concat方法

- (RACSignal *)concat:(RACSignal *)signal {
    return [[RACSignal createSignal:^(id<RACSubscriber> subscriber) {

        [self subscribeNext:^(id x) {
            [subscriber sendNext:x];
        } error:^(NSError *error) {
            [subscriber sendError:error];
        } completed:^{
            [signal subscribe:subscriber];
        }];
    }] setNameWithFormat:@"[%@] -concat: %@", self.name, signal];
}

当原始信号completed后 subcribe contact的信号

-zipWith方法

(RACSignal *)zipWith:(RACSignal *)signal
将两个信号值进行zip 即每次发出一个为RACTuple值为[signal1value, signal2value]的值当其中一个error或者completed即停止zipSignal

信号的创建

RACSignal的createSignal方法

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

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

signal保存了didSubscribe并在每次有订阅者订阅当前信号时都会执行一遍，向订阅者发送消息

RACSignal类簇

RACSignal拥有不同功能的子类

RACDynamicSignal：用于 + createSignal:

RACEmptySignal 用于 + empty

+ (RACSignal *)empty {
    return [[[self alloc] init] setNameWithFormat:@"+empty"];

}

- (RACDisposable *)subscribe:(id<RACSubscriber>)subscriber {

    return [RACScheduler.subscriptionScheduler schedule:^{

        [subscriber sendCompleted];

    }];

}

RACReturnSignal 用于 + return

+ (RACSignal *)return:(id)value {
    RACReturnSignal *signal = [[self alloc] init];

      signal->_value = value;

      return signal;

}

//将value简单保存 在有其它订阅者时 向订阅者发送value

- (RACDisposable *)subscribe:(id<RACSubscriber>)subscriber {

        NSCParameterAssert(subscriber != nil);

        return [RACScheduler.subscriptionScheduler schedule:^{

            [subscriber sendNext:self.value];

            [subscriber sendCompleted];

        }];

}

RACErrorSignal 用于 + error

+ (RACSignal *)error:(NSError *)error {
    RACErrorSignal *signal = [[self alloc] init];

    signal->_error = error;

#ifdef DEBUG

    [signal setNameWithFormat:@"+error: %@", error];

#else

    signal.name = @"+error:";

#endif

    return signal;

}

- (RACDisposable *)subscribe:(id<RACSubscriber>)subscriber {

       return [RACScheduler.subscriptionScheduler schedule:^{

    [subscriber sendError:self.error];

}];

}