Golang语言情怀-第30期 Go 语言设计模式 观察者

//Subject 观察目标类
type Subject struct {
    state    int
    observer *list.List
}

//NewSubject 实例化观察目标
func NewSubject() *Subject {
    return &Subject{
        state:    0,
        observer: list.New(),
    }
}

//GetState 获取观察目标状态值
func (s *Subject) GetState() int {
    return s.state
}

//SetState 设置观察目标状态值
func (s *Subject) SetState(st int) {
    s.state = st
    //通知观察者
    s.NotifyAllObserver()
}

//Attach 将观察者绑定到自己
func (s *Subject) Attach(ob Observer) {
    s.observer.PushBack(ob)
}

//NotifyAllObserver 通知所有观察值
func (s *Subject) NotifyAllObserver() {
    for i := s.observer.Front(); i != nil; i = i.Next() {
        i.Value.(Observer).Update()
    }
}

//Observer 观察者抽象接口
type Observer interface {
    Update()
}

//BinaryObserver 二进制观察者类
type BinaryObserver struct {
    subject *Subject
}

//NewBinaryObserver 实例化二进制观察者类
func NewBinaryObserver() *BinaryObserver {
    return &BinaryObserver{}
}

//Attach 将二进制观察者绑定到观察目标
func (bo *BinaryObserver) Attach(sub *Subject) {
    bo.subject = sub
    bo.subject.Attach(bo) //观察目标将本观察者加入更新链
}

//Update 二进制观察者接受被观察目标的更新信息
func (bo *BinaryObserver) Update() {
    fmt.Printf("Binary String: %b \n", bo.subject.GetState())
}

func ObserverTest(t *testing.T) {
    subject := NewSubject()

    hexOB := NewHexObserver()
    DecOB := NewDecimalistmObserver()
    binayOB := NewBinaryObserver()

    hexOB.Attach(subject)
    DecOB.Attach(subject)
    binayOB.Attach(subject)

    fmt.Println("First state change: 8")
    subject.SetState(8)
    fmt.Println("First state change: 15")
    subject.SetState(15)
}