如何使用 Reflect 套件根據返回或參數類型以程式設計方式選擇 Go 中的函數？

<code class="go">package main

import (
    "fmt"
    "reflect"
)

func main() {
    funcs := make([]interface{}, 3, 3) // Using interface{} to allow any kind of function
    funcs[0] = func(a int) int { return a + 1 } // Good: takes int, returns int
    funcs[1] = func(a string) int { return len(a) } // Good: returns int
    funcs[2] = func(a string) string { return ":(" } // Bad: returns string

    for _, fi := range funcs {
        f := reflect.ValueOf(fi)
        functype := f.Type()
        good := false
        for i := 0; i < functype.NumIn(); i++ {
            if functype.In(i).String() == "int" {
                good = true // Yes, there is an int input
                break
            }
        }
        for i := 0; i < functype.NumOut(); i++ {
            if functype.Out(i).String() == "int" {
                good = true // Yes, there is an int output
                break
            }
        }
        if good {
            fmt.Println(f)
        }
    }
}</code>