add generator and observer

Author: tensor-programming

generator/main.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+func fib(n int) chan int {
+	out := make(chan int)
+
+	go func() {
+		defer close(out)
+		for i, j := 0, 1; i < n; i, j = i+j, i {
+			out <- i
+		}
+
+	}()
+
+	return out
+}
+
+// 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
+
+func main() {
+	for x := range fib(10000000) {
+		fmt.Println(x)
+	}
+}

observer/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+type (
+	Event struct {
+		data int
+	}
+
+	Observer interface {
+		NotifyCallback(Event)
+	}
+
+	Subject interface {
+		AddListener(Observer)
+		RemoveListener(Observer)
+		Notify(Event)
+	}
+
+	eventObserver struct {
+		id   int
+		time time.Time
+	}
+
+	eventSubject struct {
+		observers sync.Map
+	}
+)
+
+func (e *eventObserver) NotifyCallback(event Event) {
+	fmt.Printf("Observer: %d Recieved: %d after %v\n", e.id, event.data, time.Since(e.time))
+}
+
+func (s *eventSubject) AddListener(obs Observer) {
+	s.observers.Store(obs, struct{}{})
+}
+
+func (s *eventSubject) RemoveListener(obs Observer) {
+	s.observers.Delete(obs)
+}
+
+func (s *eventSubject) Notify(event Event) {
+	s.observers.Range(func(key interface{}, value interface{}) bool {
+		if key == nil || value == nil {
+			return false
+		}
+
+		key.(Observer).NotifyCallback(event)
+		return true
+	})
+
+}
+
+func fib(n int) chan int {
+	out := make(chan int)
+
+	go func() {
+		defer close(out)
+		for i, j := 0, 1; i < n; i, j = i+j, i {
+			out <- i
+		}
+
+	}()
+
+	return out
+}
+
+// 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
+
+func main() {
+	n := eventSubject{
+		observers: sync.Map{},
+	}
+
+	t := time.Now()
+
+	var obs1 = eventObserver{id: 1, time: t}
+	var obs2 = eventObserver{id: 2, time: t}
+	n.AddListener(&obs1)
+	n.AddListener(&obs2)
+
+	go func() {
+		select {
+		case <-time.After(time.Millisecond * 10):
+			n.RemoveListener(&obs1)
+		}
+	}()
+
+	for x := range fib(100000) {
+		n.Notify(Event{data: x})
+	}
+
+}