RAC的fileter和ignore

数量计算——filter：

// 过滤效果
// 通过判断条件来过滤符合条件的信号值
[[[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
  [subscriber sendNext:@"11"];
  [subscriber sendNext:@"2222"];
  [subscriber sendNext:@"3333"];
  [subscriber sendNext:@"55"];
  [subscriber sendCompleted];
  return [RACDisposable disposableWithBlock:^{
    NSLog(@"完成...");
  }];
}] filter:^BOOL(NSString *value) {
  return value.length > 2;
}] subscribeNext:^(id x) {
  NSLog(@"subscribeNext:%@",x);
}] dispose];
// 结果：2222、3333

// 忽略某一项条件，取反
// 可以跟filter达到同等效果的ignore：
// 值不等于1的时候就返回这个值
[[[[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
  [subscriber sendNext:@"11"];
  [subscriber sendNext:@"2222"];
  [subscriber sendNext:@"3333"];
  [subscriber sendNext:@"55"];
  [subscriber sendCompleted];
  return [RACDisposable disposableWithBlock:^{
    NSLog(@"完成...");
  }];
}] ignore:@1] subscribeNext:^(id x) {
  NSLog(@"subscribeNext:%@",x);
}] dispose];

2021-04-15 11:16:30.589031+0800 XXXXXX[3487:1041151] [DYMTLInitPlatform] platform initialization successful

2021-04-15 11:16:31.647022+0800 XXXXXX[3487:1041029] subscribeNext:11

2021-04-15 11:16:31.647104+0800 XXXXXX[3487:1041029] subscribeNext:2222

2021-04-15 11:16:31.647216+0800 XXXXXX[3487:1041029] subscribeNext:3333

2021-04-15 11:16:31.647236+0800 XXXXXX[3487:1041029] subscribeNext:55

2021-04-15 11:16:31.648315+0800 XXXXXX[3487:1041029] 完成...