# 验证码服务

中间件 captcha 用于为 [Macaron 实例](/zh-cn/core_concepts.md#macaron-shi-li) 提供验证码服务。

* [GitHub](https://github.com/go-macaron/captcha)
* [API 文档](https://gowalker.org/github.com/go-macaron/captcha)

### 下载安装

```bash
go get github.com/go-macaron/captcha
```

## 使用示例

想要使用该中间件，您必须同时使用 [cache](https://github.com/go-macaron/docs/tree/f112eb7b968ef7236b6731b5b4561f3f56c9194c/zh-CN/middlewares/cache/README.md) 中间件。

```go
// main.go
import (
    "github.com/go-macaron/cache"
    "github.com/go-macaron/captcha"
    "gopkg.in/macaron.v1"
)

func main() {
    m := macaron.Classic()
    m.Use(cache.Cacher())
    m.Use(captcha.Captchaer())

    m.Get("/", func(ctx *macaron.Context, cpt *captcha.Captcha) string {
        if cpt.VerifyReq(ctx.Req) {
            return "valid captcha"
        }
        return "invalid captcha"
    })

    m.Run()
}
```

```markup
<!-- templates/hello.tmpl -->
{{.Captcha.CreateHtml}}
```

## 自定义选项

该服务允许接受一个参数来进行自定义选项（[`captcha.Options`](https://gowalker.org/github.com/go-macaron/captcha#Options)）：

```go
// ...
m.Use(captcha.Captchaer(captcha.Options{
    // 获取验证码图片的 URL 前缀，默认为 "/captcha/"
    URLPrefix:            "/captcha/",
    // 表单隐藏元素的 ID 名称，默认为 "captcha_id"
    FieldIdName:        "captcha_id",
    // 用户输入验证码值的元素 ID，默认为 "captcha"
    FieldCaptchaName:    "captcha",
    // 验证字符的个数，默认为 6
    ChallengeNums:        6,
    // 验证码图片的宽度，默认为 240 像素
    Width:                240,
    // 验证码图片的高度，默认为 80 像素
    Height:                80,
    // 验证码过期时间，默认为 600 秒
    Expiration:            600,
    // 用于存储验证码正确值的 Cache 键名，默认为 "captcha_"
    CachePrefix:        "captcha_",
}))
// ...
```


---

# 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://go-macaron.com/zh-cn/middlewares/captcha.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.