Merge pull request #24 from bvwells/mediator

Implement mediator design pattern #13

Author: bvwells

README.md

@@ -65,7 +65,7 @@ Name       | Description                               | Status
 [`Command`](./behavioral/command.go) | Encapsulate a request as an object, thereby allowing for the parameterization of clients with different requests, and the queuing or logging of requests. It also allows for the support of undoable operations. | Implemented
 [`Interpreter`](./behavioral/interpreter.go) | Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language. |
 [`Iterator`](./behavioral/iterator.go) | Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation. | Implemented
-[`Mediator`](./behavioral/mediator.go) | Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it allows their interaction to vary independently. |
+[`Mediator`](./behavioral/mediator.go) | Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it allows their interaction to vary independently. | Implemented
 [`Memento`](./behavioral/memento.go) | Without violating encapsulation, capture and externalize an object's internal state allowing the object to be restored to this state later. |
 [`Observer`](./behavioral/observer.go) | Define a one-to-many dependency between objects where a state change in one object results in all its dependents being notified and updated automatically. | Implemented
 [`State`](./behavioral/state.go) | Allow an object to alter its behavior when its internal state changes. The object will appear to change its class. | Implemented

behavioral/mediator.go

@@ -1 +1,73 @@
 package behavioral
+
+import "fmt"
+
+// WildStallion describes an interface for a Wild Stallion band member.
+type WildStallion interface {
+	SetMediator(mediator Mediator)
+}
+
+// Bill describes Bill S. Preston, Esquire.
+type Bill struct {
+	mediator Mediator
+}
+
+// SetMediator sets the mediator.
+func (b *Bill) SetMediator(mediator Mediator) {
+	b.mediator = mediator
+}
+
+// Respond responds.
+func (b *Bill) Respond() {
+	fmt.Fprintf(outputWriter, "Bill: What?\n")
+	b.mediator.Communicate("Bill")
+}
+
+// Ted describes Ted "Theodore" Logan.
+type Ted struct {
+	mediator Mediator
+}
+
+// SetMediator sets the mediator.
+func (t *Ted) SetMediator(mediator Mediator) {
+	t.mediator = mediator
+}
+
+// Talk talks through mediator.
+func (t *Ted) Talk() {
+	fmt.Fprintf(outputWriter, "Ted: Bill?\n")
+	t.mediator.Communicate("Ted")
+}
+
+// Respond responds.
+func (t *Ted) Respond() {
+	fmt.Fprintf(outputWriter, "Ted: Strange things are afoot at the Circle K.\n")
+}
+
+// Mediator describes the interface for communicating between Wild Stallion band members.
+type Mediator interface {
+	Communicate(who string)
+}
+
+// ConcreateMediator describes a mediator between Bill and Ted.
+type ConcreateMediator struct {
+	Bill
+	Ted
+}
+
+// NewMediator creates a new ConcreateMediator.
+func NewMediator() *ConcreateMediator {
+	mediator := &ConcreateMediator{}
+	mediator.Bill.SetMediator(mediator)
+	mediator.Ted.SetMediator(mediator)
+	return mediator
+}
+
+// Communicate communicates between Bill and Ted.
+func (m *ConcreateMediator) Communicate(who string) {
+	if who == "Ted" {
+		m.Bill.Respond()
+	} else if who == "Bill" {
+		m.Ted.Respond()
+	}
+}

behavioral/mediator_test.go

@@ -0,0 +1,22 @@
+package behavioral
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMediator(t *testing.T) {
+
+	bufferOutputWriter := outputWriter
+	outputWriter = new(bytes.Buffer)
+	defer func() { outputWriter = bufferOutputWriter }()
+
+	mediator := NewMediator()
+	mediator.Ted.Talk()
+
+	assert.Equal(t, "Ted: Bill?\n"+
+		"Bill: What?\n"+
+		"Ted: Strange things are afoot at the Circle K.\n", outputWriter.(*bytes.Buffer).String())
+}