Reactive Cocoa：只订阅新值

Question

我是 Reactive 的新手 Cocoa。我想要实现的是每次属性值更改时都会收到通知。但是，我不想在属性设置为相同值时收到通知。这是一些代码：

self.testProperty = 0;
[[RACObserve(self, self.testProperty) skip:1] subscribeNext:^(id x) {
    NSLog(@"Did Change: %@", x);
}];

self.testProperty = 1;
self.testProperty = 1;
self.testProperty = 1;
self.testProperty = 1;
self.testProperty = 1;

这就是我在控制台输出中得到的

> Did Change: 1
> Did Change: 1
> Did Change: 1
> Did Change: 1
> Did Change: 1

我预计 "Did change" 只会打印一次，而不是五次。有没有办法只订阅新值？

Answer 1

有一个方法，distinctUntilChanged:

[[[RACObserve(self, self.testProperty) 
  skip:1]
  distinctUntilChanged]
  subscribeNext:^(id x) {
    NSLog(@"Did Change: %@", x);
}];

Reactive Cocoa：只订阅新值

Reactive Cocoa: subscribe only to new values

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