• 1.1, fileter

    RACSubject *subject = [RACSubject subject];
    [[subject filter:^BOOL(NSString *value) {
        return value.length > 2;
    }] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
    
    
    [subject sendNext:@"132"];
    ```
    
* 1.2, ignore,忽略掉需要忽略的值
   

RACSubject *subject01 = [RACSubject subject];
[[subject01 ignore:@(3)] subscribeNext:^(id x) {
    NSLog(@"%@",x);
}];

[subject01 sendNext:@3];

    
* 1.3, take，从前面一共取几次，也就是可以接受几次数据
    

RACSubject *subject02 = [RACSubject subject];
[[subject02 take:2] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];

[subject02 sendNext:@"第一次"];
[subject02 sendNext:@"第二次"];
[subject02 sendNext:@"第三次"];
[subject02 sendNext:@"第四次"];

 
* 1.4, takeLast,从后往前一共取几次数据，需要发送完成信息

RACSubject *subject03 = [RACSubject subject];
[[subject03 takeLast:2] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];

[subject03 sendNext:@"第一次"];
[subject03 sendNext:@"第二次"];
[subject03 sendNext:@"第三次"];
[subject03 sendNext:@"第四次"];
[subject03 sendCompleted];
```

• 1.5, takeUntil,执行直到遇到until后面的那个信号

    RACSubject *subject04 = [RACSubject subject];
    RACSubject *endSignal = [RACSubject subject];
    
    [[subject04 takeUntil:endSignal] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
    
    [subject04 sendNext:@"第一次"];
    [subject04 sendNext:@"第二次"];
    [endSignal sendCompleted];
    [subject04 sendNext:@"第三次"];
    [subject04 sendNext:@"第四次"];
    
    ```
    
* 1.6, distinctUntilChanged,过滤掉重复的值

RACSubject *subject05 = [RACSubject subject];

[[subject05 distinctUntilChanged] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];

[subject05 sendNext:@"第一次"];
[subject05 sendNext:@"第二次"];
[subject05 sendNext:@"第二次"];//这次是重复的，所以就不会接受这个数据
[subject05 sendNext:@"第三次"];
[subject05 sendNext:@"第四次"];

 
* 1.7，skip，跳过前面几个值

 ```
 RACSubject *subject06 = [RACSubject subject];
 
 [[subject06 skip:1] subscribeNext:^(id x) {
     NSLog(@"%@", x);
 }];
 
 [subject06 sendNext:@"第一次"];
 [subject06 sendNext:@"第二次"];
 [subject06 sendNext:@"第三次"];
 [subject06 sendNext:@"第四次"];