flyweight.go

//main package has examples shown
// in Go Data Structures and algorithms book
package main

// importing fmt package
import (
	"fmt"
)

//DataTransferObjectFactory struct
type DataTransferObjectFactory struct {
	pool map[string]DataTransferObject
}

//DataTransferObjectFactory class method getDataTransferObject
func (factory DataTransferObjectFactory) getDataTransferObject(dtoType string) DataTransferObject {

	var dto = factory.pool[dtoType]

	if dto == nil {

		fmt.Println("new DTO of dtoType: " + dtoType)
		switch dtoType {
		case "customer":
			factory.pool[dtoType] = Customer{id: "1"}
		case "employee":
			factory.pool[dtoType] = Employee{id: "2"}
		case "manager":
			factory.pool[dtoType] = Manager{id: "3"}
		case "address":
			factory.pool[dtoType] = Address{id: "4"}
		}

		dto = factory.pool[dtoType]

	}

	return dto
}

// DataTransferObject interface
type DataTransferObject interface {
	getId() string
}

//Customer struct
type Customer struct {
	id   string //sequence generator
	name string
	ssn  string
}

// Customer class method getId
func (customer Customer) getId() string {
	//fmt.Println("getting customer Id")
	return customer.id

}

//Employee struct
type Employee struct {
	id   string
	name string
}

//Employee class method getId
func (employee Employee) getId() string {
	return employee.id
}

//Manager struct
type Manager struct {
	id   string
	name string
	dept string
}

//Manager class method getId
func (manager Manager) getId() string {
	return manager.id
}

//Address struct
type Address struct {
	id          string
	streetLine1 string
	streetLine2 string
	state       string
	city        string
}

//Address class method getId
func (address Address) getId() string {
	return address.id
}

//main method
func main() {
	var factory = DataTransferObjectFactory{make(map[string]DataTransferObject)}
	var customer DataTransferObject = factory.getDataTransferObject("customer")

	fmt.Println("Customer ", customer.getId())
	var employee DataTransferObject = factory.getDataTransferObject("employee")
	fmt.Println("Employee ", employee.getId())
	var manager DataTransferObject = factory.getDataTransferObject("manager")
	fmt.Println("Manager", manager.getId())
	var address DataTransferObject = factory.getDataTransferObject("address")
	fmt.Println("Address", address.getId())
}