the-way-to-go_ZH_CN/eBook/18.5.md

# 18.5 接口

（1）如何检测一个值`v`是否实现了接口`Stringer`：

```go
if v, ok := v.(Stringer); ok {
    fmt.Printf("implements String(): %s\n", v.String())
}
```

（2）如何使用接口实现一个类型分类函数：
    
```go
func classifier(items ...interface{}) {
    for i, x := range items {
        switch x.(type) {
        case bool:
            fmt.Printf("param #%d is a bool\n", i)
        case float64:
            fmt.Printf("param #%d is a float64\n", i)
        case int, int64:
            fmt.Printf("param #%d is an int\n", i)
        case nil:
            fmt.Printf("param #%d is nil\n", i)
        case string:
            fmt.Printf("param #%d is a string\n", i)
        default:
            fmt.Printf("param #%d’s type is unknown\n", i)
        }
    }
}
```

## 链接

- [目录](directory.md)
- 上一节：[结构体](18.4.md)
- 下一节：[函数](18.6.md)