Interface implementations not required anymore

Author: badu

README.md

@@ -10,21 +10,19 @@ and the handler is having the following signature:
 
 `func OnMyEventOccurred(event InterestingEvent)`
 
-where `InterestingEvent` has to be a struct which has to implement two methods:
-
-`type InterestingEvent struct{}`
+The event producer will simply do:
 
-`func (e InterestingEvent) EventID() string{ return "MyUniqueName" }`
+`bus.Pub(InterestingEvent{})`
 
-where the string which represents the name of the event has to be unique across the event system.
+Optional, to allow the bus to spin a goroutine for dispatching events, implement the following interface:
 
 `func (e InterestingEvent) Async() bool{ return true }`
 
-where we signal that the event will be passed to the listeners by spinning up a goroutine.
+or
 
-The event producer will simply do:
+`func (e *InterestingEvent) Async() bool{ return true }`
 
-`bus.Pub(InterestingEvent{})`
+By default, the bus is using sync events : waits for listeners to complete their jobs before calling the next listener.
 
 Usage : `go get github.com/badu/bus`
 
@@ -100,10 +98,6 @@ Inside the `test_scenarios` folder, you can find the following scenarios:
 
    I am sure that you will find this technique interesting and having a large number of applications.
 
-   An important note is about not forgetting to implement the `EventID() string` correctly, as incorrect naming triggers
-   panic (expecting one type of event, but receiving another). To exemplify this, just alter the return of
-   this [function](https://github.com/badu/bus/blob/main/test_scenarios/request-reply-callback/events/main.go#L24).
-
 4. Request Reply with Cancellation
 
    Last but, not least, this is an example about providing `context.Context` along the publisher subscriber chain.
@@ -120,7 +114,9 @@ Inside the `test_scenarios` folder, you can find the following scenarios:
    because changing properties that represents the `reply` would not be reflected. Also, when using `sync.WaitGroup`
    inside your event struct, always use method receivers and pass the event as pointer, otherwise you will be passing a
    lock by value (which is `sync.Locker`).
-2. be careful if you don't want to use pointers for events, but you still need to pass values from the listener to the
+3. be careful if you don't want to use pointers for events, but you still need to pass values from the listener to the
    dispatcher. You should still have at least one property of that event that is a pointer (see events
    in `request reply with cancellation` for example). Same technique can be applied when you need `sync.Waitgroup` to be
    passed around with an event that is being sent by value, not by pointer.
+4. you can override the event name (which is by default, built using `fmt.Sprintf("%T", yourEvent)`) you need to
+   implement `EventID() string` interface.

bench_test.go

@@ -11,22 +11,10 @@ type Uint32SyncEvent struct {
 	u uint32
 }
 
-func (u Uint32SyncEvent) EventID() string {
-	return "Uint32SyncEvent"
-}
-
-func (u Uint32SyncEvent) Async() bool {
-	return false
-}
-
 type Uint32AsyncEvent struct {
 	u uint32
 }
 
-func (u Uint32AsyncEvent) EventID() string {
-	return "Uint32AsyncEvent"
-}
-
 func (u Uint32AsyncEvent) Async() bool {
 	return true
 }

main.go

@@ -1,33 +1,38 @@
 package bus
 
 import (
+	"fmt"
 	"sync"
 	"sync/atomic"
 )
 
-var mapper sync.Map // holds key (event id, typed string) versus topic values
+var mapper sync.Map // holds key (event name - string) versus topic values
 
-// internal interface that all the events must implement
-type iEvent interface {
+// we allow developers to override event names. They should be careful about name collisions
+type iEventName interface {
 	EventID() string //
-	Async() bool     // if returns true, this event will be triggered by spinning a goroutine
+}
+
+// if developers implement this interface, we're spinning a goroutine if the event says it is async
+type iAsync interface {
+	Async() bool
 }
 
 // Listener is being returned when you subscribe to a topic, so you can unsubscribe or access the parent topic
-type Listener[T iEvent] struct {
+type Listener[T any] struct {
 	parent   *Topic[T]     // so we can call unsubscribe from parent
 	callback func(event T) // the function that we're going to call
 }
 
 // Topic keeps the subscribers of one topic
-type Topic[T iEvent] struct {
+type Topic[T any] struct {
 	subs      []*Listener[T] // list of listeners
 	rwMu      sync.RWMutex   // guards subs
 	lisnsPool sync.Pool      // a pool of listeners
 }
 
 // NewTopic creates a new topic for a specie of events
-func NewTopic[T iEvent]() *Topic[T] {
+func NewTopic[T any]() *Topic[T] {
 	result := &Topic[T]{}
 	result.lisnsPool.New = func() any {
 		return &Listener[T]{
@@ -90,19 +95,26 @@ func (s *Listener[T]) Topic() *Topic[T] {
 // Pub allows you to publish an event in that topic
 func (b *Topic[T]) Pub(event T) {
 	b.rwMu.RLock()
-	for topic := range b.subs {
-		if event.Async() {
-			go b.subs[topic].callback(event)
+
+	isAsync := false
+	switch m := any(event).(type) {
+	case iAsync:
+		isAsync = m.Async()
+	}
+
+	for sub := range b.subs {
+		if isAsync {
+			go b.subs[sub].callback(event)
 			continue
 		}
 
-		b.subs[topic].callback(event)
+		b.subs[sub].callback(event)
 	}
 	b.rwMu.RUnlock()
 }
 
 // Bus is being returned when you subscribe, so you can manually Unsub
-type Bus[T iEvent] struct {
+type Bus[T any] struct {
 	listener *Listener[T]
 	stop     atomic.Uint32 // flag for unsubscribing after receiving one event
 }
@@ -115,11 +127,20 @@ func (o *Bus[T]) Unsub() {
 }
 
 // SubUnsub can be used if you need to unsubscribe immediately after receiving an event, by making your function return true
-func SubUnsub[T iEvent](callback func(event T) bool) *Bus[T] {
+func SubUnsub[T any](callback func(event T) bool) *Bus[T] {
 	var event T
-	topic, ok := mapper.Load(event.EventID())
+
+	key := ""
+	switch m := any(event).(type) {
+	case iEventName:
+		key = m.EventID()
+	default:
+		key = fmt.Sprintf("%T", event)
+	}
+
+	topic, ok := mapper.Load(key)
 	if !ok || topic == nil {
-		topic, _ = mapper.LoadOrStore(event.EventID(), NewTopic[T]())
+		topic, _ = mapper.LoadOrStore(key, NewTopic[T]())
 	}
 
 	var result Bus[T]
@@ -140,11 +161,20 @@ func SubUnsub[T iEvent](callback func(event T) bool) *Bus[T] {
 }
 
 // Sub subscribes a callback function to listen for a specie of events
-func Sub[T iEvent](callback func(event T)) *Bus[T] {
+func Sub[T any](callback func(event T)) *Bus[T] {
 	var event T
-	topic, ok := mapper.Load(event.EventID())
+
+	key := ""
+	switch m := any(event).(type) {
+	case iEventName:
+		key = m.EventID()
+	default:
+		key = fmt.Sprintf("%T", event)
+	}
+
+	topic, ok := mapper.Load(key)
 	if !ok || topic == nil {
-		topic, _ = mapper.LoadOrStore(event.EventID(), NewTopic[T]())
+		topic, _ = mapper.LoadOrStore(key, NewTopic[T]())
 	}
 
 	var result Bus[T]
@@ -160,10 +190,19 @@ func Sub[T iEvent](callback func(event T)) *Bus[T] {
 }
 
 // Pub publishes an event which will be dispatched to all listeners
-func Pub[T iEvent](event T) {
-	topic, ok := mapper.Load(event.EventID())
+func Pub[T any](event T) {
+	key := ""
+	switch m := any(event).(type) {
+	case iEventName:
+		key = m.EventID()
+	default:
+		key = fmt.Sprintf("%T", event)
+	}
+
+	topic, ok := mapper.Load(key)
 	if !ok || topic == nil { // create new topic, even if there are no listeners (otherwise we will have to panic)
-		topic, _ = mapper.LoadOrStore(event.EventID(), NewTopic[T]())
+		topic, _ = mapper.LoadOrStore(key, NewTopic[T]())
 	}
+
 	topic.(*Topic[T]).Pub(event)
 }

test_scenarios/factory-request-reply/events/main.go

@@ -7,11 +7,6 @@ import (
 	"github.com/badu/bus/test_scenarios/factory-request-reply/prices"
 )
 
-const (
-	InventoryGRPCClientRequestEventType = "InventoryGRPCClientRequestEvent"
-	PricesGRPCClientRequestEventType    = "PricesGRPCClientRequestEvent"
-)
-
 type InventoryGRPCClientRequestEvent struct {
 	wg     sync.WaitGroup
 	Conn   Closer // should be *grpc.ClientConn, but we're avoiding the import
@@ -24,10 +19,6 @@ func NewInventoryGRPCClientRequestEvent() *InventoryGRPCClientRequestEvent {
 	return &result
 }
 
-func (i *InventoryGRPCClientRequestEvent) EventID() string {
-	return InventoryGRPCClientRequestEventType
-}
-
 func (i *InventoryGRPCClientRequestEvent) Async() bool {
 	return true // this one is async
 }
@@ -52,14 +43,6 @@ func NewPricesGRPCClientRequestEvent() *PricesGRPCClientRequestEvent {
 	return &result
 }
 
-func (p *PricesGRPCClientRequestEvent) EventID() string {
-	return PricesGRPCClientRequestEventType
-}
-
-func (p *PricesGRPCClientRequestEvent) Async() bool {
-	return false // this one is sync
-}
-
 func (p *PricesGRPCClientRequestEvent) WaitReply() {
 	p.wg.Wait()
 }

test_scenarios/fire-and-forget/events/main.go

@@ -1,21 +1,10 @@
 package events
 
-const (
-	UserRegisteredEventType string = "UserRegisteredEvent"
-	SMSRequestEventType     string = "SMSRequestEvent"
-	SMSSentEventType        string = "SmsSentEvent"
-	DummyEventType          string = "DummyEvent"
-)
-
 type UserRegisteredEvent struct {
 	UserName string
 	Phone    string
 }
 
-func (e UserRegisteredEvent) EventID() string {
-	return UserRegisteredEventType
-}
-
 func (e UserRegisteredEvent) Async() bool {
 	return true
 }
@@ -25,10 +14,6 @@ type SMSRequestEvent struct {
 	Message string
 }
 
-func (e SMSRequestEvent) EventID() string {
-	return SMSRequestEventType
-}
-
 func (e SMSRequestEvent) Async() bool {
 	return true
 }
@@ -38,21 +23,14 @@ type SMSSentEvent struct {
 	Status  string
 }
 
-func (e SMSSentEvent) EventID() string {
-	return SMSSentEventType
-}
-
 func (e SMSSentEvent) Async() bool {
 	return true
 }
 
 type DummyEvent struct {
-}
-
-func (e *DummyEvent) EventID() string {
-	return DummyEventType
+	AlteredAsync bool
 }
 
 func (e *DummyEvent) Async() bool {
-	return true
+	return e.AlteredAsync
 }

test_scenarios/fire-and-forget/main_test.go

@@ -2,15 +2,22 @@ package fire_and_forget
 
 import (
 	"context"
+	"fmt"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/badu/bus"
 	"github.com/badu/bus/test_scenarios/fire-and-forget/audit"
+	"github.com/badu/bus/test_scenarios/fire-and-forget/events"
 	"github.com/badu/bus/test_scenarios/fire-and-forget/notifications"
 	"github.com/badu/bus/test_scenarios/fire-and-forget/users"
 )
 
+func OnDummyEvent(event *events.DummyEvent) {
+	fmt.Println("dummy event async ?", event.Async())
+}
+
 func TestUserRegistration(t *testing.T) {
 	var sb strings.Builder
 
@@ -19,6 +26,8 @@ func TestUserRegistration(t *testing.T) {
 	notifications.NewEmailService(&sb)
 	audit.NewAuditService(&sb)
 
+	bus.Sub(OnDummyEvent)
+
 	userSvc.RegisterUser(context.Background(), "Badu", "+40742222222")
 
 	<-time.After(500 * time.Millisecond)

test_scenarios/fire-and-forget/users/service.go

@@ -10,6 +10,7 @@ import (
 
 type ServiceImpl struct {
 	sb *strings.Builder
+	c  int
 }
 
 func NewService(sb *strings.Builder) ServiceImpl {
@@ -18,6 +19,7 @@ func NewService(sb *strings.Builder) ServiceImpl {
 }
 
 func (s *ServiceImpl) RegisterUser(ctx context.Context, name, phone string) {
+	s.c++
 	bus.Pub(events.UserRegisteredEvent{UserName: name, Phone: phone})
-	bus.Pub(&events.DummyEvent{}) // nobody listens on this one
+	bus.Pub(&events.DummyEvent{AlteredAsync: s.c%2 == 0}) // nobody listens on this one
 }

test_scenarios/request-reply-callback/events/main.go

@@ -1,11 +1,5 @@
 package events
 
-import (
-	"fmt"
-)
-
-const RequestEventType = "RequestEvent"
-
 type RequestEvent[T any] struct {
 	Payload  T
 	Callback func() (*T, error)
@@ -19,11 +13,6 @@ func NewRequestEvent[T any](payload T) *RequestEvent[T] {
 	}
 }
 
-func (i *RequestEvent[T]) EventID() string {
-	var t T
-	return fmt.Sprintf("%s%T", RequestEventType, t)
-}
-
 func (i *RequestEvent[T]) Async() bool {
 	return true // this one is async
 }