在 2016年9月23日星期五 UTC+8下午12:13:04，Lax Clarke写道：
>
> How would someone create a function like len ?
>
> func Len(s []interface{}) would not work because compiler complains of
> type mismatch if you call it with an integer slice (for example)
>
> Thanks
>
[]interface{} is a concrete type, which is miss-match with []int{}. You may
use interface{} as formal parameter but call the function with a
[]interface{}
package main
import "fmt"
import "reflect"
func Len(v interface{}) int {
var length int
switch reflect.TypeOf(v).Kind() {
// return the length of slice, use
// func (v Value) Len() int
case reflect.Slice:
length = reflect.ValueOf(v).Len()
// return the length of int, or whatever you want
case reflect.Int:
// ...
}
return length
}
type X struct {
a, b int
}
func main() {
a := []int{1,2,3} // a typed slice, all elements' type is concrete (int)
b := []interface{}{1, "11", 12.345, X{1, 2}} // still a typed slice, all
elements' type is dynamic (interface)
fmt.Println(Len(a), Len(b))
}
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