mediator

README

Behavioral » Mediator

Elements

• Mediator - interface to mediate between colleagues
• Concrete Mediator - transfer messages between colleague
• Colleague Class - communicate to the mediator to communicate with other object

Description

It defined an object that encapsulate the manner of how a set of objects interact each others. This patterns also solve the problem of coupling delegating to the mediator the responsibility to manipulate objects.

Implementation

In the following implementation we consider the mediator as a sort of teacher. The teacher will teaches to students and all students will learn.

type Student interface {
	Class() string
	Learn(message string)
	Learned() string
}

type Mediator interface {
	TeachesTo(c *Student)
	Spread(messqger string)
}

A class mate implements the interface Student. It learn something and tell what he or she have learned. In this mediator implementation students dont speak each others.

type ClassMate struct {
	name        string
	lastMessage string
	forum       string
}

func (a *ClassMate) Class() string {
	return a.forum
}

func (a *ClassMate) Learn(message string) {
	a.lastMessage = message
}

func (a *ClassMate) Learned() string {
	return a.lastMessage
}

Finally the teacher. Teach spread knowledge and decide the list of students to teach to.

type Teacher struct {
	learners []Student
}

func (m *Teacher) TeachesTo(c Student) {
	m.learners = append(m.learners, c)
}

func (m *Teacher) Spread(message string) {
	for _, a := range m.learners {
		a.Learn(message)
	}
}

All works inside the main function. When the teacher say something, a student learn.

func NewClassMate(name string) Student {
	return &ClassMate{name, "meeting 1", ""}
}

func main() {

	teacher := Teacher{}

	student := NewClassMate("Mario")

	teacher.TeachesTo(student)
	teacher.TeachesTo(NewClassMate("Demo"))
	teacher.TeachesTo(NewClassMate("Mattia"))
	teacher.TeachesTo(NewClassMate("Simone"))

	fmt.Println(len(teacher.attendees))
	fmt.Println(student.Class())

	eteacher.Spread("Message sent to everyone")

	fmt.Println(student.Learned()) // Message sent to everyone

}

Last but not least a test to prove that student really learned lesson!

func TestStudentLearn(t *testing.T) {
	teacher := Teacher{}
	student := NewClassMate("Mario")
	teacher.TeachesTo(student)
	teacher.Spread("Message sent to everyone")
	if student.Learned() != "Message sent to everyone" {
		t.Error("Student should learn")
	}
}