Golang Value Object tests

main.go

package main

import (
	"fmt"
	"regexp"
)

// EmailAddress Value Object
type EmailAddress string

// Value Render the EmailAddress as simple string by default
func (e EmailAddress) Value() string {
	return string(e)
}

// FromString Static "constructor"
func FromString(value string) (EmailAddress, error) {
	var e EmailAddress
	match, _ := regexp.MatchString(`^[a-z0-9._%+\-]+@[a-z0-9.\-]+\.[a-z]{2,4}$`, value)
	if !match {
		return e, fmt.Errorf("%s is not a valid email address", value)
	}
	return EmailAddress(value), nil
}

// Host returns the host part of an email address
func (e EmailAddress) Host() string {
	return regexp.MustCompile(`([a-z0-9._%+\-]+)@([a-z0-9.\-]+\.[a-z]{2,4})$`).FindStringSubmatch(string(e))[2]
}

func main() {
	email, err := FromString("foo@bar.com")
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(email.Host())
}