如何在不知道键/值类型的情况下测试接口{}是否为映射？

Question

Although it is possible to test whether an interface{} is a map of known key/value type:

func TypeTest(thing interface{}) {
    switch thing.(type) {
    case map[string]string:
        fmt.Println("map string string")
    case map[string]interface{}:
        fmt.Println("map string")
    case map[interface{}]interface{}:
        fmt.Println("map")
    case interface{}:
        fmt.Println("interface")
    default:
        fmt.Println("unknown")
    }
}
TypeTest(map[string]string{"a": "1"}) // "map string string"
TypeTest(map[string]int{"a": 1}) // "interface" !!!

But what if I just want to know whether an interface{} is a map or not, without worrying about its key/value type?

Answer 1

You can use the reflect package for this.

package main

import "fmt"
import "reflect"

func main() {
    m := make(map[string]int)

    fmt.Printf("%v
", isMap(m))
}

func isMap(m interface{}) bool {
    rt := reflect.TypeOf(m)
    return rt.Kind() == reflect.Map
}