# just

**创建 `Observable` 发出唯一的一个元素**

![](https://4217506537-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MWj545abP2yK86-qksJ%2Fsync%2F57c6129d2c40f3ffad29b800ba2d5c27ac9e518d.png?generation=1616819384752922\&alt=media)

**just** 操作符将某一个元素转换为 `Observable`。

## 演示

一个序列只有唯一的元素 **0**：

```swift
let id = Observable.just(0)
```

它相当于：

```swift
let id = Observable<Int>.create { observer in
    observer.onNext(0)
    observer.onCompleted()
    return Disposables.create()
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://3440217568.gitbook.io/rxswift/decision_tree/just.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.