[TOC] ## 設計模式 ### 訂閱發布 <details> <summary> main.go</summary> ``` type ( subscriber chan interface{} // 訂閱者為一個管道 topicFunc func(v interface{}) bool // 主題為一個過濾器 ) // 發布者對象 type Publisher struct { m sync.RWMutex // 讀寫鎖 buffer int // 訂閱隊列的緩存大小 timeout time.Duration // 發布超時時間 subscribers map[subscriber]topicFunc // 訂閱者信息 } // 構建一個發布者對象, 可以設置發布超時時間和緩存隊列的長度 func NewPublisher(publishTimeout time.Duration, buffer int) *Publisher { return &Publisher{ buffer: buffer, timeout: publishTimeout, subscribers: make(map[subscriber]topicFunc), } } // 添加一個新的訂閱者，訂閱過濾器篩選后的主題 func (p *Publisher) SubscribeTopic(topic topicFunc) subscriber { ch := make(subscriber, p.buffer) p.m.Lock() p.subscribers[ch] = topic p.m.Unlock() return ch } // 退出訂閱 func (p *Publisher) Evict(sub subscriber) { p.m.Lock() defer p.m.Unlock() delete(p.subscribers, sub) close(sub) } // 添加一個新的訂閱者，訂閱全部主題 func (p *Publisher) Subscribe() subscriber { return p.SubscribeTopic(nil) } // 發布一個主題 func (p *Publisher) Publish(v interface{}) { p.m.RLock() defer p.m.RUnlock() var wg sync.WaitGroup for sub, topic := range p.subscribers { wg.Add(1) go p.sendTopic(sub, topic, v, &wg) } wg.Wait() } // 關閉發布者對象，同時關閉所有的訂閱者管道。 func (p *Publisher) Close() { p.m.Lock() defer p.m.Unlock() for sub := range p.subscribers { delete(p.subscribers, sub) close(sub) } } // 發送主題，可以容忍一定的超時 func (p *Publisher) sendTopic( sub subscriber, topic topicFunc, v interface{}, wg *sync.WaitGroup, ) { defer wg.Done() if topic != nil && !topic(v) { return } select { case sub <- v: case <-time.After(p.timeout): } } ``` </details> <br /> <details> <summary> main.go</summary> ``` func main() { p := NewPublisher(100*time.Millisecond, 10) defer p.Close() all := p.Subscribe() golang := p.SubscribeTopic(func(v interface{}) bool { if s, ok := v.(string); ok { return strings.Contains(s, "golang") } return false }) p.Publish("hello, world!") p.Publish("hello, golang!") go func() { for msg := range all { fmt.Println("all:", msg) } } () go func() { for msg := range golang { fmt.Println("golang:", msg) } } () // 運行一定時間后退出 time.Sleep(3 * time.Second) } ``` </details> <br />