EventBus

README

EventBus

Package EventBus is the little and lightweight eventbus with async compatibility for GoLang.

Installation

Make sure that Go is installed on your computer. Type the following command in your terminal:

go get github.com/asaskevich/EventBus

After it the package is ready to use.

Import package in your project

Add following line in your *.go file:

import "github.com/asaskevich/EventBus"

If you unhappy to use long EventBus, you can do something like this:

import (
	evbus "github.com/asaskevich/EventBus"
)

Example

func calculator(a int, b int) {
	fmt.Printf("%d\n", a + b)
}

func main() {
	bus := EventBus.New();
	bus.Subscribe("main:calculator", calculator);
	bus.Publish("main:calculator", 20, 40);
	bus.Unsubscribe("main:calculator");
}

Implemented methods

• New()
• Subscribe()
• SubscribeOnce()
• HasCallback()
• Unsubscribe()
• Publish()
• SubscribeAsync()
• SubscribeOnceAsync()
• WaitAsync()

New()

New returns new EventBus with empty handlers.

bus := EventBus.New();

Subscribe(topic string, fn interface{}) error

Subscribe to a topic. Returns error if fn is not a function.

func Handler() { ... }
...
bus.Subscribe("topic:handler", Handler)

SubscribeOnce(topic string, fn interface{}) error

Subscribe to a topic once. Handler will be removed after executing. Returns error if fn is not a function.

func HelloWorld() { ... }
...
bus.SubscribeOnce("topic:handler", HelloWorld)

Unsubscribe(topic string) error

Remove callback defined for a topic. Returns error if there are no callbacks subscribed to the topic.

bus.Unsubscribe("topic:handler");

HasCallback(topic string) bool

Returns true if exists any callback subscribed to the topic.

Publish(topic string, args ...interface{})

Publish executes callback defined for a topic. Any addional argument will be tranfered to the callback.

func Handler(str string) { ... }
...
bus.Subscribe("topic:handler", Handler)
...
bus.Publish("topic:handler", "Hello, World!");

SubscribeAsync(topic string, fn interface{}, transactional bool)

Subscribe to a topic with an asyncrhonous callback. Returns error if fn is not a function.

func slowCalculator(a, b int) {
	time.Sleep(3 * time.Second)
	fmt.Printf("%d\n", a + b)
}

bus := EventBus.New()
bus.SubscribeAsync("main:slow_calculator", slowCalculator, false)
	
bus.Publish("main:slow_calculator", 20, 60)
	
fmt.Println("start: do some stuff while waiting for a result")
fmt.Println("end: do some stuff while waiting for a result") 
	
bus.WaitAsync() // wait for all async callbacks to complete
	
fmt.Println("do some stuff after waiting for result") 

Transactional determines whether subsequent callbacks for a topic are run serially (true) or concurrently(false)

SubscribeOnceAsync(topic string, args ...interface{})

SubscribeOnceAsync works like SubscribeOnce except the callback to executed asynchronously

WaitAsync()

WaitAsync waits for all async callbacks to complete.

Notes

Documentation is available here: godoc.org. Full information about code coverage is also available here: EventBus on gocover.io.

Support

If you do have a contribution for the package feel free to put up a Pull Request or open Issue.

Special thanks to contributors

• Brian Downs
• Dominik Schulz
• bennAH

Documentation

Index

• type EventBus
  • func New() *EventBus
  • func (bus *EventBus) HasCallback(topic string) bool
  • func (bus *EventBus) Publish(topic string, args ...interface{})
  • func (bus *EventBus) Subscribe(topic string, fn interface{}) error
  • func (bus *EventBus) SubscribeAsync(topic string, fn interface{}, transactional bool) error
  • func (bus *EventBus) SubscribeOnce(topic string, fn interface{}) error
  • func (bus *EventBus) SubscribeOnceAsync(topic string, fn interface{}) error
  • func (bus *EventBus) Unsubscribe(topic string) error
  • func (bus *EventBus) WaitAsync()

Types

type EventBus

type EventBus struct {
	// contains filtered or unexported fields
}

EventBus - box for handlers and callbacks.

func New

func New() *EventBus

New returns new EventBus with empty handlers.

func (*EventBus) HasCallback

func (bus *EventBus) HasCallback(topic string) bool

HasCallback returns true if exists any callback subscribed to the topic.

func (*EventBus) Publish

func (bus *EventBus) Publish(topic string, args ...interface{})

Publish executes callback defined for a topic. Any addional argument will be tranfered to the callback.

func (*EventBus) Subscribe

func (bus *EventBus) Subscribe(topic string, fn interface{}) error

Subscribe subscribes to a topic. Returns error if `fn` is not a function.

func (*EventBus) SubscribeAsync

func (bus *EventBus) SubscribeAsync(topic string, fn interface{}, transactional bool) error

SubscribeAsync subscribes to a topic with an asynchronous callback Transactional determines whether subsequent callbacks for a topic are run serially (true) or concurrently (false) Returns error if `fn` is not a function.

func (*EventBus) SubscribeOnce

func (bus *EventBus) SubscribeOnce(topic string, fn interface{}) error

SubscribeOnce subscribes to a topic once. Handler will be removed after executing. Returns error if `fn` is not a function.

func (*EventBus) SubscribeOnceAsync

func (bus *EventBus) SubscribeOnceAsync(topic string, fn interface{}) error

SubscribeOnceAsync subscribes to a topic once with an asyncrhonous callback Handler will be removed after executing. Returns error if `fn` is not a function.

func (*EventBus) Unsubscribe

func (bus *EventBus) Unsubscribe(topic string) error

Unsubscribe removes callback defined for a topic. Returns error if there are no callbacks subscribed to the topic.

func (*EventBus) WaitAsync

func (bus *EventBus) WaitAsync()

WaitAsync waits for all async callbacks to complete