是否可以知道Go中函数的返回值类型？

Question

For example, I want to do something like this,

package main

import (
    "fmt"
    "reflect"
)

func main() {
    var f func(int) int
    v := reflect.ValueOf(f)
    fmt.Println(v.ReturnType() == reflect.TypeOf(1)) // => true
}

ReturnType method doesn't exist in reflect package. My question is, can I implement such a function without using cgo.

Answer 1

Rather than using reflect.ValueOf(f) try reflect.TypeOf(f). The Type type has two relevant methods named NumOut and Out(int). To get the types of all return values in order, you can use the following loop

typ := reflect.TypeOf(f)

for i := 0; i < typ.NumOut(); i++ {
    returnType := typ.Out(i)
    // do something with returnType
}

If you're certain your function only has one return value, you can always get it with Out(0), the standard disclaimers about making sure your input is correct apply.