> For the complete documentation index, see [llms.txt](https://gitbook.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook.com/docs/documentation/zh/creating-content/variables-and-expressions.md).

# 变量与表达式

使用变量，你可以创建可复用的文本，这些文本可以在 [表达式](/docs/documentation/zh/creating-content/formatting/inline.md#expressions) 以及 [自适应内容的条件](/docs/documentation/zh/zhan-dian-fang-wen-quan-xian/adaptive-content/adapting-your-content.md#working-with-the-condition-editor).

如果你在内容中多次重复相同的名称、短语或版本号，你可以创建一个 **变量** 来帮助保持所有这些实例同步且准确——这在你需要更新它们，或者它们很复杂且经常被误输入时很有用。

你可以创建作用域限定为单个页面或单个章节的变量。

### 创建新变量

要创建新变量，请点击 **资源库** 在编辑已打开的 [变更请求](/docs/documentation/zh/collaboration/change-requests.md)时的目录中。然后，点击 **变量**.

你可以使用顶部的切换开关，查看并创建仅适用于你当前所在页面，或当前章节内所有页面的变量。

点击 **创建变量** 将会打开一个模态窗口，你可以为变量命名并赋值。

点击 **添加变量** 以保存你的变量。

<figure><img src="/files/cc6d4f3771aad0927e4468738f15c5dfb8cba040" alt="A GitBook screenshot showing the Add variables screen. The variable Name box has been filled with the text ‘latest_version’ and the Value box has been filled with the text ‘v3.04.1’"><figcaption><p>你可以将变量添加到单个页面或整个章节中。当你更新变量的值时，它的每个实例都会随之更新。</p></figcaption></figure>

{% hint style="info" %}
变量名称必须以字母开头，并且可以包含字母、数字和下划线。
{% endhint %}

### 在内容中使用变量

变量可以在一个 [表达式](/docs/documentation/zh/creating-content/formatting/inline.md#expressions) 表达式中被引用和使用——你可以将其内联插入到内容中。插入表达式后，双击它即可打开表达式编辑器。

{% hint style="info" %}
表达式只能用于文档的页面内容中。它们不能用于页面标题或页面元数据。
{% endhint %}

在页面下定义的变量可在 `page.vars` 对象下访问。同样，在整个章节范围内定义的变量可在 `space.vars` 对象下访问。

{% hint style="info" %}
在表达式中，章节范围的变量位于 `space.vars` —— GitBook API 将章节表示为 `space` 对象。
{% endhint %}

<figure><img src="/files/fa14f5ad70d98845bcc22d2f52ce414a9fe28622" alt="A GitBook screenshot showing an expression block within the editor. The expression editor is open below it and the ‘space.vars.latest_version’ variable has been selected"><figcaption><p>你可以通过表达式将变量添加到内容中。表达式编辑器提供自动补全选项，帮助你找到所需的变量。</p></figcaption></figure>

### 更新变量

你可以在变更请求中随时更新变量。更新其值会同步更新所有引用它的表达式块中的值。一旦变更请求合并，已更改的变量就会在任何已发布的网站上生效。


---

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