snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/basic/6-cqrs-ordered-events/subscribers.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"context"
+	"log/slog"
+	"sync"
+)
+
+type SubscriberReadModel struct {
+	subscribers map[string]string // map[subscriberID]email
+	lock        sync.RWMutex
+}
+
+func NewSubscriberReadModel() *SubscriberReadModel {
+	return &SubscriberReadModel{
+		subscribers: make(map[string]string),
+	}
+}
+
+func (m *SubscriberReadModel) OnSubscribed(ctx context.Context, event *SubscriberSubscribed) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	m.subscribers[event.SubscriberId] = event.Email
+
+	slog.Info(
+		"Subscriber added",
+		"subscriber_id", event.SubscriberId,
+		"email", event.Email,
+	)
+
+	return nil
+}
+
+func (m *SubscriberReadModel) OnUnsubscribed(ctx context.Context, event *SubscriberUnsubscribed) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	delete(m.subscribers, event.SubscriberId)
+
+	slog.Info(
+		"Subscriber removed",
+		"subscriber_id", event.SubscriberId,
+	)
+
+	return nil
+}
+
+func (m *SubscriberReadModel) OnEmailUpdated(ctx context.Context, event *SubscriberEmailUpdated) error {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	m.subscribers[event.SubscriberId] = event.NewEmail
+
+	slog.Info(
+		"Subscriber updated",
+		"subscriber_id", event.SubscriberId,
+		"email", event.NewEmail,
+	)
+
+	return nil
+}
+
+func (m *SubscriberReadModel) GetSubscriberCount() int {
+	m.lock.RLock()
+	defer m.lock.RUnlock()
+	return len(m.subscribers)
+}