anonymous-function.go

package main

import "fmt"

type Blacklist func(string) bool

// function with parameter of function type
func registerUser(name string, isBlacklist Blacklist) {
	if isBlacklist(name) {
		fmt.Println("You are blocked")
	} else {
		fmt.Println("Welcome", name)
	}
}

// normal function
func isBlacklisted(name string) bool {
	blacklistUser := []string{"admin", "root", "sys"}
	for _, user := range blacklistUser {
		if user == name {
			return true
		}
	}
	return false
}

func main() {
	// anonymous function
	// for simple way to write function

	// regular function
	registerUser("admin", isBlacklisted)

	// anonymous function #1 (for simple way)
	registerUser("guest", func(user string) bool {
		blacklistedUser := []string{"admin", "root", "sys"}
		for _, name := range blacklistedUser {
			if user == name {
				return true
			}
		}
		return false
	})

	// anonymous function #2 other style
	blacklisted := func(user string) bool {
		blacklistedUser := []string{"admin", "root", "sys"}
		for _, name := range blacklistedUser {
			if user == name {
				return true
			}
		}
		return false
	}

	registerUser("root", blacklisted)

}