# distinctUntilChanged

**阻止 `Observable` 发出相同的元素**

![](/files/-MWlwQv1S3AJc7lyjFaC)

**distinctUntilChanged** 操作符将阻止 `Observable` 发出相同的元素。如果后一个元素和前一个元素是相同的，那么这个元素将不会被发出来。如果后一个元素和前一个元素不相同，那么这个元素才会被发出来。

## 演示

```swift
let disposeBag = DisposeBag()

Observable.of("🐱", "🐷", "🐱", "🐱", "🐱", "🐵", "🐱")
    .distinctUntilChanged()
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)
```

**输出结果：**

```swift
🐱
🐷
🐱
🐵
🐱
```


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