typesafebuilder.gotype safe builder in GoType Safe Builder in Go

typesafebuilder.go

/*
 * It becomes painfully obvious why this pattern is NOT embraced by the Go community.
 * Just to be painfully clear, DO NOT DO THIS!
 */
package main

import (
	"fmt"
)

type Person struct {
	FirstName string
	LastName string
	EmailAddress string
}

type PersonBuilderFirstName interface {
	FirstName(string) PersonBuilderLastName
}

type PersonBuilderLastName interface {
	LastName(string) PersonBuilderEmailAddress
}

type PersonBuilderEmailAddress interface {
	EmailAddress(string) Person
}

func PersonBuilder() PersonBuilderFirstName {
	return &personBuilder{
		firstName: "",
		lastName: "",
		emailAddress: "",
	}
}

type personBuilder struct {
	firstName string
	lastName string
	emailAddress string
}

func (pb *personBuilder) FirstName(firstName string) PersonBuilderLastName {
	//TODO: validate firstName to fail fast
	pb.firstName = firstName
	return pb
}

func (pb *personBuilder) LastName(lastName string) PersonBuilderEmailAddress {
	//TODO: validate lastName fail fast
	pb.lastName = lastName
	return pb
}

func (pb *personBuilder) EmailAddress(emailAddress string) Person {
	//TODO: validate emailAddress fail fast
	pb.emailAddress = emailAddress
	//TODO: or validate them all in one giant block here and lose context of where the invalid data came from
	return Person{
		FirstName: pb.firstName,
		LastName: pb.lastName,
		EmailAddress: pb.emailAddress,
	}
}

func main() {
	pb := PersonBuilder()
	person := pb.FirstName("John").LastName("Doe").EmailAddress("johndoe@example.com")
	fmt.Println(person)
}