ReactiveCocoa—RACSubject and RACReplaySubject

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RACSubject

继承于RACSignal

// RACSubject:底层实现和RACSignal不一样。
1.调用subscribeNext订阅信号，只是把订阅者保存起来，并且订阅者的nextBlock已经赋值了。
2.调用sendNext发送信号，遍历刚刚保存的所有订阅者，一个一个调用订阅者的nextBlock
3.调用sendNext发送信号，不会保留原来的历史值，把最新的数据传递给订阅者

RACSubject *subect = [RACSubject subject];
[subect sendNext:@"数学"];

[subect subscribeNext:^(id x) {
    NSLog(@"我订阅了:%@",x);
}];
[subect sendNext:@"语文"];

[subect subscribeNext:^(id x) {
   NSLog(@"你订阅了:%@",x);
}];
[subect sendNext:@"历史"];

2016-10-12 18:02:13.298 ReactiveCocoa基础02[60479:413849] 我订阅了:语文
2016-10-12 18:02:13.298 ReactiveCocoa基础02[60479:413849] 我订阅了:历史
2016-10-12 18:02:13.299 ReactiveCocoa基础02[60479:413849] 你订阅了:历史

通常用来代替代理

ViewController.m

@interface ViewController ()

@end

@implementation ViewController


- (IBAction)click:(id)sender {

    NextViewController *nextVC = [[NextViewController alloc] init];

    // 设置代理信号
    nextVC.subect = [RACSubject subject];

    // 订阅代理信号
    [nextVC.subect subscribeNext:^(id x) {
        //点击了第二个界面
        NSLog(@"%@",x);
    }];

    // 跳转到第二个控制器
    [self presentViewController:nextVC animated:YES completion:nil];

}

NextViewController.h

@interface NextViewController : UIViewController

@property(nonatomic ,strong)RACSubject *subect;

@end

NextViewController.m

@interface NextViewController ()

@property (nonatomic ,strong)UIButton  *button;
@end

@implementation NextViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor yellowColor];

    [self.view addSubview:self.button];
}

//懒加载按钮
- (UIButton *)button{

    if (!_button) {
       _button = [UIButton buttonWithType:UIButtonTypeCustom];
        _button.frame = CGRectMake(0, 0, 150, 50);
        _button.backgroundColor = [UIColor whiteColor];
        [_button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
        [_button setTitle:@"点击返回" forState:UIControlStateNormal];
        [_button addTarget:self action:@selector(notice) forControlEvents:UIControlEventTouchUpInside];
        _button.center = self.view.center;
    }

    return _button;
}

//点击事件
-(void)notice{

    [self dismissViewControllerAnimated:YES completion:nil];

    if (self.subect) {
        [self.subect sendNext:@"点击了第二个界面"];
    }
}

RACReplaySubject

继承于RACSubject

区别：
RACReplaySubject可以先发送信号，在订阅信号，RACSubject就不可以
同时会保留原来的历史数据，等待订阅者激活时接收数据

RACReplaySubject *replaySubject = [RACReplaySubject subject];

// 2.发送信号
[replaySubject sendNext:@1];
[replaySubject sendNext:@2];

// 3.订阅信号
[replaySubject subscribeNext:^(id x) {

    NSLog(@"第一个订阅者接收到的数据%@",x);
}];
[replaySubject sendNext:@3];

// 订阅信号
[replaySubject subscribeNext:^(id x) {

    NSLog(@"第二个订阅者接收到的数据%@",x);
}];
[replaySubject sendNext:@4];

2016-10-12 18:11:46.766 ReactiveCocoa基础02[60909:424986] 第一个订阅者接收到的数据1
2016-10-12 18:11:46.766 ReactiveCocoa基础02[60909:424986] 第一个订阅者接收到的数据2
2016-10-12 18:11:46.767 ReactiveCocoa基础02[60909:424986] 第一个订阅者接收到的数据3
2016-10-12 18:11:46.767 ReactiveCocoa基础02[60909:424986] 第二个订阅者接收到的数据1
2016-10-12 18:11:46.767 ReactiveCocoa基础02[60909:424986] 第二个订阅者接收到的数据2
2016-10-12 18:11:46.768 ReactiveCocoa基础02[60909:424986] 第二个订阅者接收到的数据3
2016-10-12 18:11:46.782 ReactiveCocoa基础02[60909:424986] 第一个订阅者接收到的数据4
2016-10-12 18:11:46.782 ReactiveCocoa基础02[60909:424986] 第二个订阅者接收到的数据4

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