ReactiveCocoa学习之二

ReactiveCocoa信号(RACStream (Operations)文件中)操作像Swift里面的一些高阶函数一样有map,flattenMap,reduce, filter等操作。

1. map

(Returns a new stream with the mapped values.)

 [signale map:^id(id value) {
 1⃣️
 return [NSString stringWithFormat:@"输出:%@",value];2⃣️
 }] subscribeNext:^(id x) {
 NSLog(@"090909----->%@",x);3⃣️
 }];
 

其中:
1⃣️：传入一个block类型,返回id类型的对象,参数是value
2⃣️：value就是源信号的内容，直接拿到源信号的内容做处理。并返回相关id
3⃣️：x表示经过处理后的value值

2. flattenMap

(Returns a new stream which represents the combined streams resulting from mapping block.)

 [signal flattenMap:^RACStream *(id value) {
 1⃣️
 return [RACSignal return:[NSString stringWithFormat:@"输出09090：%@",value]]; 2⃣️
 }] subscribeNext:^(id x) {
 NSLog(@"%@",x); 3⃣️
 }];
 ]
 

其中：
1⃣️：传入一个block，block类型是返回值RACStream，参数value
2⃣️：参数value就是源信号的内容，拿到源信号的内容做处理。注意这里返回的是一个RACStream信号类,不是id对象。
3⃣️:输出经过处理的value内容。

3. reduce

(Returns a signal which sends the results from each invocation of reduceBlock.)

 RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id subscriber) {
 [subscriber sendNext:@"A"];
 [subscriber sendCompleted];
 return nil;
 }];
 RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id subscriber) {
 
 
    [subscriber sendNext:@"B"];
    [subscriber sendCompleted];
    return nil;
}];
RACSignal *reduceSignal = [RACSignal combineLatest:@[signalA,signalB] reduce:^id(NSString *x,NSString *y){
    return [NSString stringWithFormat:@"%@ %@",x,y];
}];
[reduceSignal subscribeNext:^(id x) {
    NSLog(@"%@",x); ---->A B
}];
 
 

其中:
常见的用法，（先组合在聚合）。combineLatest:(id)signals reduce:(id (^)())reduceBlock
reduce中的block简介:
reduceblcok中的参数，有多少信号组合，reduceblcok就有多少参数，每个参数就是之前信号发出的内容
reduceblcok的返回值：聚合信号之后的内容。

4. filter

Filters out values in the receiver that don't pass the given test. This corresponds to the Where method in Rx.
Returns a new stream with only those values that passed.
过滤不符合要求的信号，返回符合要求的信号。

 [[textFiled.rac_textSignal filter:^BOOL(NSString *value) {
 return value.length>3;
 }] subscribeNext:^(id x) {
 NSLog(@"%@",x);
 }];
 当输入框的内容长度>3时，才有输出。