add observer mode

10_observer/oberser.go

@@ -0,0 +1,47 @@
+package observer
+
+import "fmt"
+
+type Subject struct {
+	observers []Observer
+	context   string
+}
+
+func NewSubject() *Subject {
+	return &Subject{
+		observers: make([]Observer, 0),
+	}
+}
+
+func (s *Subject) Attach(o Observer) {
+	s.observers = append(s.observers, o)
+}
+
+func (s *Subject) notify() {
+	for _, o := range s.observers {
+		o.Update(s)
+	}
+}
+
+func (s *Subject) UpdateContext(context string) {
+	s.context = context
+	s.notify()
+}
+
+type Observer interface {
+	Update(*Subject)
+}
+
+type Reader struct {
+	name string
+}
+
+func NewReader(name string) *Reader {
+	return &Reader{
+		name: name,
+	}
+}
+
+func (r *Reader) Update(s *Subject) {
+	fmt.Printf("%s receive %s\n", r.name, s.context)
+}

10_observer/oberser_test.go

@@ -0,0 +1,17 @@
+package observer
+
+func ExampleObserver() {
+	subject := NewSubject()
+	reader1 := NewReader("reader1")
+	reader2 := NewReader("reader2")
+	reader3 := NewReader("reader3")
+	subject.Attach(reader1)
+	subject.Attach(reader2)
+	subject.Attach(reader3)
+
+	subject.UpdateContext("observer mode")
+	// Output:
+	// reader1 receive observer mode
+	// reader2 receive observer mode
+	// reader3 receive observer mode
+}