gvre / event

An Event Dispatcher Library written in Go

Event Dispatcher Library

The Event Dispatcher library provides the necessary functionality that allows your application components to communicate with each other in a decoupled way, by dispatching events and listening to them.

Creating an Event Listener

The way to listen to an event is to register an event listener.

dispatcher := event.NewDispatcher()
// OR var dispatcher event.Dispatcher
// Note: Make sure to pass a pointer to the dispatcher,
// instead of copying it, if you need to pass it to a function.
dispatcher.On("event", func(ev interface{}) bool {
    if e, ok := ev.(*MyAppEvent); ok {
        // handle event
    }

    // return false to stop event propagation
    return true
})

Dispatching an Event

In general, a single dispatcher, which holds all listeners, is needed. When an event is dispatched, the dispatcher notifies all listeners registered with that event:

dispatcher := event.NewDispatcher()
dispatcher.On("event", func(ev interface{}) bool {
    if e, ok := ev.(*MyAppEvent); ok {
        // handle event
    }

    // return false to stop event propagation
    return true
})

ev := &MyAppEvent{}
dispatcher.Dispatch("event", ev)

Example

package main

import (
	"fmt"

	"github.com/gvre/event"
)

type UserCreatedEvent struct {
	ID   int
	Name string
}

func main() {
	dispatcher := event.NewDispatcher()
	dispatcher.On("user.created", func(ev interface{}) bool {
		if e, ok := ev.(*UserCreatedEvent); ok {
			fmt.Println(e)
		}

		return true
	})

	ev := &UserCreatedEvent{
		ID:   1,
		Name: "user",
	}
	dispatcher.Dispatch("user.created", ev)
}

The above code in playground: https://play.golang.org/p/4ag-48koyop

Naming Conventions

The event name can be any string, but optionally follows the following conventions:

• Use only lowercase letters, numbers, dots (.) and underscores (_);
• Prefix names with a namespace followed by a dot (e.g. user.*);
• End names with a verb that indicates what action has been taken (e.g. user.created).

License

• MIT