constuctor-with-optional-params.go

package main

import mgo "gopkg.in/mgo.v2"

// Persist is a persisting dependency
type Persist interface {
	Insert() (err error)
	Update() (err error)
	Remove() (err error)
}

// Mongo is a concrete Persist example
type Mongo struct {
	collection *mgo.Collection
}

func init() {
	// Mongo.SetCollection()
}

// Insert an object to the collection
func (mongo *Mongo) Insert() (err error) {
	err = mongo.collection.Insert()
	return
}

// Insert an object to the collection
func (mongo *Mongo) Update() (err error) {
	//err = mongo.collection.Update()
	return err
}

// Insert an object to the collection
func (mongo *Mongo) Remove() (err error) {
	err = mongo.collection.Remove()
	return err
}

// private because we have to use a factory like pattern as a "constructor"
type user struct {
	Persist Persist // inject as dependency?
	name    string
	mail    string
}

// Insert
func (userObject user) Insert() (err error) {
	err = userObject.Persist.Insert()
	return
}

// User is a constructor like construct with optional parameters (as function)
func User(options ...func(*user) error) *user {
	userObject := new(user)
	// Run the options that in turn can set any public property
	for _, function := range options {
		// function shuold set something
		function(userObject)
	}

	// Persistence is mandatory set the default if not set via option function
	if userObject.Persist == nil {
		userObject.Persist = new(Mongo)
	}

	return userObject
}