ex6.go

package ecommerce

import (
	"strconv"
)

type order struct {
	pid productID
	cid customerID
}

type productID struct {
	id int64
}

// some methods on productID struct

type customerID struct {
	id int64
}

// some methods on customerID struct

type orderID struct {
	id int64
}

func (oid orderID) String() string {
	return strconv.FormatInt(oid.id, 10)
}

// some other methods on orderID struct

func CreateOrder(pid int64, cid int64) order {
	return order{
		pid: productID{pid}, cid: customerID{cid},
	}
}

func (o order) Submit() (orderID, error) {
	// do some logic

	return orderId{int64(3252345234)}, nil
}