01. 观察者模式
<p>观察者模式用于触发联动。</p>
<p>一个对象的改变会触发其它观察者的相关动作，而此对象无需关心连动对象的具体实现。</p>
<h4>obserser.go</h4>
<pre><code>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)
}</code></pre>
<h4>obserser_test.go</h4>
<pre><code>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
}</code></pre>