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message source pure

Package message provides a simple message broker implementation.

Overview

Package message provides a simple message broker implementation.

The message broker is a Pub/Sub one. It implements two different interfaces, `Publisher` and `Subscriber`, which are also defined within this package.

Published messages contain the topic where they are published and optional message data.

Subscribe to an event:

Example
1broker := message.NewBroker()
2subID, err := broker.Subscribe("EventName", func(msg message.Message) {
3   println("EventName has been triggered")
4   println(msg.Data)
5})
6if err != nil {
7   panic(err)
8}

Unsubscribe from an event:

Example
1unsubscribed, err := broker.Unsubscribe("EventName", subID)
2if err != nil {
3   panic(err)
4}
5
6if !unsubscribed {
7   panic("subscription not found")
8}

Publish an event:

Example
1err := broker.Publish("EventName", "Example event data")
2if err != nil {
3   panic(err)
4}

Constants 1

const TopicAll 

1const TopicAll Topic = "*"
source

TopicAll defines a topic for all types of message. This topic can be used to subscribe to message for all topics.

Variables 1

var ErrInvalidTopic, ErrRequiredCallback, ErrRequiredSubscriptionID, ErrRequiredTopic 

 1var (
 2	// ErrInvalidTopic is triggered when an invalid topic is used.
 3	ErrInvalidTopic = errors.New("invalid topic")
 4
 5	// ErrRequiredCallback is triggered when subscribing without a callback.
 6	ErrRequiredCallback = errors.New("message callback is required")
 7
 8	// ErrRequiredSubscriptionID is triggered when unsubscribing without an ID.
 9	ErrRequiredSubscriptionID = errors.New("message sibscription ID is required")
10
11	// ErrRequiredTopic is triggered when (un)subscribing without a topic.
12	ErrRequiredTopic = errors.New("message topic is required")
13)
source

Functions 1

func NewBroker 

1func NewBroker() *Broker
source

NewBroker creates a new message broker.

Types 6

type Broker

struct 
1type Broker struct {
2	callbacks avl.Tree // string(topic) -> *ulist.List(Callback)
3}
source

Broker is a message broker that handles subscriptions and message publishing.

Methods on Broker

func Publish

method on Broker 
1func (b Broker) Publish(topic Topic, data any) error
source

Publish publishes a message for a topic.

func Subscribe

method on Broker 
1func (b *Broker) Subscribe(topic Topic, cb Callback) (id int, _ error)
source

Subscribe subscribes to messages published for a topic. It returns the callback ID within the topic.

func Topics

method on Broker 
1func (b Broker) Topics() []Topic
source

Topics returns the list of current subscription topics.

func Unsubscribe

method on Broker 
1func (b *Broker) Unsubscribe(topic Topic, id int) (unsubscribed bool, _ error)
source

Unsubscribe unsubscribes a callback from a message topic. ID is the callback ID within the topic, returned on subscription.

type Callback

func 
1type Callback func(Message)
source

Callback defines a type for message callbacks.

type Message

struct 
1type Message struct {
2	// Topic is the message topic.
3	Topic Topic
4
5	// Data contains optional message data.
6	Data any
7}
source

Message defines a type for published messages.

type Publisher

interface 
1type Publisher interface {
2	// Publish publishes a message for a topic.
3	Publish(_ Topic, data any) error
4}
source

Publisher defines an interface for message publishers.

type Subscriber

interface 
1type Subscriber interface {
2	// Subscribe subscribes to messages published for a topic.
3	// It returns the callback ID within the topic.
4	Subscribe(Topic, Callback) (id int, _ error)
5
6	// Unsubscribe unsubscribes a callback from a message topic.
7	// ID is the callback ID within the topic, returned on subscription.
8	Unsubscribe(_ Topic, id int) (unsubscribed bool, _ error)
9}
source

Subscriber defines an interface for message subscribers.

type Topic

ident 
1type Topic string
source

Topic defines a type for message topics.

Imports 4

Source Files 6