> For the complete documentation index, see [llms.txt](https://3440217568.gitbook.io/rxswift/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://3440217568.gitbook.io/rxswift/decision_tree/distinctuntilchanged.md).

# distinctUntilChanged

**阻止 `Observable` 发出相同的元素**

![](https://4217506537-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MWj545abP2yK86-qksJ%2Fsync%2Fa19da00733218b7f316bb557f1016d9148759fe1.png?generation=1616819395642955\&alt=media)

**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
🐱
🐷
🐱
🐵
🐱
```