error handling

errors.go

@@ -0,0 +1,21 @@
+package goevent
+
+import "fmt"
+
+type EventNotDefined struct {
+	eventName string
+}
+
+func newEventNotDefined(name string) *EventNotDefined {
+	return &EventNotDefined{
+		eventName: name,
+	}
+}
+
+func (e *EventNotDefined) Error() string {
+	return fmt.Sprintf("%s event has not been defined yet.", e.eventName)
+}
+
+func (e *EventNotDefined) EventName() string {
+	return e.eventName
+}

table.go

@@ -1,9 +1,6 @@
 package goevent
 
-import (
-	"fmt"
-	"sync"
-)
+import "sync"
 
 type Table interface {
 	On(string, interface{}) error
@@ -29,7 +26,7 @@ func (t *table) Trigger(name string, args ...interface{}) error {
 
 	ev, ok := t.events[name]
 	if !ok {
-		return fmt.Errorf("%s event has not been defined yet.", name)
+		return newEventNotDefined(name)
 	}
 
 	return ev.Trigger(args...)
@@ -53,7 +50,7 @@ func (t *table) Off(name string, f interface{}) error {
 
 	e, ok := t.events[name]
 	if !ok {
-		return fmt.Errorf("%s event has not been defined yet.", name)
+		return newEventNotDefined(name)
 	}
 
 	return e.Off(f)
@@ -61,7 +58,7 @@ func (t *table) Off(name string, f interface{}) error {
 
 func (t *table) Destroy(name string) error {
 	if _, ok := t.events[name]; !ok {
-		return fmt.Errorf("%s event has not been defined yet.", name)
+		return newEventNotDefined(name)
 	}
 	delete(t.events, name)
 	return nil