ReactiveCocoa函数响应式编程-基础篇目录：一、了解函数响应式编程二、ReactiveCocoa简介三、ReactiveCocoa集成四、ReactiveCocoa信号理解五、Reactiv

platform :ios, '8.0'
use_frameworks!     #必须添加
target 'ZSTest' do  #工程名
#pod 'ReactiveObjC' #默认导入最新的RAC版本         
end

platform :ios, '8.0'
use_frameworks!     #必须添加
target 'ZSTest' do  #工程名
pod 'ReactiveCocoa'
pod 'ReactiveObjC'  
pod 'ReactiveObjCBridge'
end

[self.userNameTxtField.rac_textSignal subscribeNext:^(NSString * _Nullable x) {
        NSLog(@"测试：%@",x);
}];

控制台打印：
2018-03-23 17:57:00.497956+0800 ZSTest[4351:263810] 测试：1
2018-03-23 17:57:00.498237+0800 ZSTest[4351:263810] 测试：12
2018-03-23 17:57:00.498375+0800 ZSTest[4351:263810] 测试：123

//创建信号
RACSignal *testSignal = [RACSignal createSignal:^RACDisposable * _Nullable(id<RACSubscriber>  _Nonnull subscriber) {
    //1.订阅者发送信号内容
    [subscriber sendNext:@"发送信号内容"];
    //2.订阅者发送信号完成的信息，不需要再发送数据时，最好发送信号完成，可以内部调起清理信号的操作。
    [subscriber sendCompleted];
    //3.创建信号的Block参数，需要返回一个RACDisposable对象 ，可以返回nil。
    //RACDisposable对象用于取消订阅信号，此block在信号完成或者错误时调用。
    RACDisposable *racDisposable = [RACDisposable disposableWithBlock:^{
       NSLog(@"信号Error或者Complete时销毁");
    }];
    return racDisposable;
}];
    
//订阅信号
[testSignal subscribeNext:^(id  _Nullable x) {
    //新变化的值
    NSLog(@"订阅信号：subscribeNext:%@",x);
} error:^(NSError * _Nullable error) {
    //信号错误，被取消订阅,被移除观察
    NSLog(@"订阅信号：Error:%@",error.description);
} completed:^{
    //信号已经完成，被取消订阅，被移除观察
    NSLog(@"订阅信号：subscribeComplete");
}];

控制台打印:
2018-03-23 17:57:00.497956+0800 ZSTest[4351:263810] 订阅信号：subscribeNext:发送信号内容
2018-03-23 17:57:00.498237+0800 ZSTest[4351:263810] 订阅信号：subscribeComplete
2018-03-23 17:57:00.498375+0800 ZSTest[4351:263810] 信号Error或者Complete时销毁

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

//RACDynamicSignal.h文件
@interface RACDynamicSignal ()
// The block to invoke for each subscriber.
@property (nonatomic, copy, readonly) RACDisposable * (^didSubscribe)(id<RACSubscriber> subscriber);
@end

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

//发送信息
- (void)sendNext:(nullable id)value;
//发送错误消息
- (void)sendError:(nullable NSError *)error;
//发送完成信息
- (void)sendCompleted;
//
- (void)didSubscribeWithDisposable:(RACCompoundDisposable *)disposable;

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

- (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;
}