EventKt

EventKt is a simple and lightweight kotlin multiplatform event bus library.

The library uses Kotlin Coroutines Flow for provide you the events. Also the library provide support for remote event publishing and listening, you can check more at the remote section.

• Principles
• Getting Started
• Examples
• Remote

Principles

The EventKt is scoped based, this means that for you publish or listen for some event you need a EventScope. The library provides a global scope GlobalEventScope.

Getting Started

repositories {
    maven {
        url = "http://nexus.devsrsouza.com.br/repository/maven-public/"
    }
}

dependencies {
    // multiplatform
    implementation("br.com.devsrsouza.eventkt:eventkt-core:0.2.0-SNAPSHOT")
}

JVM target: implementation("br.com.devsrsouza.eventkt:eventkt-core-jvm:0.2.0-SNAPSHOT")

Examples

import br.com.devsrsouza.eventkt.scopes.GlobalEventScope
import br.com.devsrsouza.eventkt.listen

data class OnSomethingHappen(val withValue: String)

GlobalEventScope.listen<OnSomethingHappen>()
    .onEach { (withValue) ->
        println("Receive my event OnSomethingHappen was triggered with value: $withValue")
    }.launchIn(myCoroutineScope)

GlobalEventScope.publish(OnSomethingHappen("Hello World!"))

Using with callback

import br.com.devsrsouza.eventkt.scopes.GlobalEventScope
import br.com.devsrsouza.eventkt.scopes.asSimple
import br.com.devsrsouza.eventkt.listen

data class OnSomethingHappen(val withValue: String)

SimpleGlobalEventScope.listen<OnSomethingHappen>(owner = this) { (withValue) ->
    println("Receive my event OnSomethingHappen was triggered with value: $withValue")
}

SimpleGlobalEventScope.publish(OnSomethingHappen("Hello World!"))

Creating your own scope

import br.com.devsrsouza.eventkt.scopes.LocalEventScope
import br.com.devsrsouza.eventkt.listen

data class OnSomethingLocallyHappen(val withValue: String)

val yourScope = LocalEventScope()

yourScope.listen<OnSomethingLocallyHappen>()
    .onEach { (withValue) ->
        println("Receive my event OnSomethingLocallyHappen was triggered with value: $withValue")
    }.launchIn(myCoroutineScope)

yourScope.publish(OnSomethingHappen("Hello Local World!"))

Listen in your coroutine scope

import br.com.devsrsouza.eventkt.scopes.GlobalEventScope
import br.com.devsrsouza.eventkt.scopes.asSimple
import br.com.devsrsouza.eventkt.listen

val singleThreadContext = newSingleThreadContext("EventReceiverThread")
val myCoroutineScope = CoroutineScope(singleThreadContext)

data class OnSomethingHappen()

val simpleEventScope = GlobalEventScope.asSimple()

simpleEventScope.listen<OnSomethingHappen>(owner = this, coroutineScope = myCoroutineScope) { (withValue) ->
    println("Receive my event in thread: ${Thread.currentThread().name}")
}

GlobalEventScope.publish(OnSomethingHappen())

In Android you could receive events directly in the Main Thread (UI Thread) using simples as well. SimpleGlobalEventScope.listen<OnSomethingHappen>(owner = this, coroutineScope = viewLifecycleOwner.lifecycleScope) {}

Unregistering callback listener

When using simple scope you should always unregister your owners on disable/destroy/stop a object that listen, like a Activity/Fragment/Service on Android

import br.com.devsrsouza.eventkt.scopes.asSimple

simpleEventScope.unregisterOwner(owner = this)

withOwner extension

import br.com.devsrsouza.eventkt.scopes.asSimple

SimpleGlobalEventScope.withOwner(this) {
    listen<OnSomethingHappen> {
        println("Yeah!")
    }
}

// unregistering
SimpleGlobalEventScope.unregister(this)

Combining EventScopes

val combinedScope: EventScope = LocalEventScope() + RedisEventScope()

Remote

EventKt is design to be used with Remote event publisher, such as Redis Pub/Sub, WebsSocket, Kafka, MQTT, AMQP etc.

Encoders

Remote event listen and publish require to your class/object to enconded and decoded, for this reason, you will need a encoder. EventKt provides a Kotlinx.serialization encoder implementation.

dependencies {
    implementation("br.com.devsrsouza.eventkt:eventkt-remote-encoder-serialization:0.2.0-SNAPSHOT")
}

Supported clients

Client	Package
Jedis/Redis (jvm)	br.com.devsrsouza.eventkt:eventkt-remote-jvm-jedis:0.2.0-SNAPSHOT
RabbitMQ/AMQP (jvm)	br.com.devsrsouza.eventkt:eventkt-remote-jvm-rabbitmq:0.2.0-SNAPSHOT
Eclipse Paho/MQTT (jvm)	br.com.devsrsouza.eventkt:eventkt-remote-jvm-paho:0.2.0-SNAPSHOT

Redis example

The project ships a Jedis Redis Client implementation (jvm only). The recommendation is to use Kotlinx.serialization encoder, in case you use it, you will need make your events @Serializable.

dependencies {
    implementation("br.com.devsrsouza.eventkt:eventkt-remote-jvm-jedis:0.2.0-SNAPSHOT")

    // encoder
    implementation("br.com.devsrsouza.eventkt:eventkt-remote-encoder-serialization:0.2.0-SNAPSHOT")
}

Usage

val subscribe = Jedis("127.0.0.1").apply { connect() }
val publisher = Jedis("127.0.0.1").apply { connect() }

val redisScope = JedisEventScope(
    StringSerializationRemoteEncoder(Json),
    subscribe,
    publisher,
    channelName = "MyProjectChannelName"
)

With this scope you can publish and listen to events from remote instances.

@Serializable
data class YourEventClass(val x: String)

redisScope.listen<YourEventClass>()
    .onEach { println(it) }
    .launchIn(GlobalScope)