closure example

main.go

// https://github.com/XTLS/Xray-core/blob/main/proxy/vmess/aead/kdf.go 实现示意
package main

import "fmt"

type caller struct {
	F   func()
	key string
}

func (c caller) Call() {
	if c.key != "" {
		fmt.Println(c.key)
	}
	c.F()
}

func newCaller(f func(), key string) *caller {
	return &caller{F: f, key: key}
}

func main() {
	callee := &caller{F: func() { fmt.Println(1) }}

	words := []string{"bb", "dd", "jj"}

	for _, word := range words {
		callee = newCaller(callee.Call, word)
	}

	callee.Call() // jj\ndd\nbb\n1\n
}