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Subscribe & Unsubscribe topics

Courier library provides the functionality of subscribing & unsubscribing topics through both service interface and MqttClient.

Subscribe/Unsubscribe through Service Interface​

interface MessageService {
    @Subscribe(topic = "topic/{id}/receive", qos = QoS.ONE)
    fun subscribe(@Path("id") identifier: String): Observable<Message>
    
    @SubscribeMultiple
    fun subscribeMultiple(@TopicMap topics: Map<String, QoS>): Observable<Message>
    
    @Unsubscribe(topics = ["topic/{id}/receive"])
    fun unsubscribe(@Path("id") identifier: String)
}
messageService.subscribe("user-id").subscribe { message ->
    print(message)
}

messageService.subscribeMultiple(mapOf("topic1" to QoS.ONE, "topic2" to QoS.TWO)).subscribe { message ->
    print(message)
}

messageService.unsubscribe("user-id")

Subscribe/Unsubscribe through MqttClient​

mqttClient.subscribe("topic1" to QoS.ZERO, "topic2" to QoS.ONE)

mqttClient.unsubscribe("topic1", "topic2")

Note : While subscribing topics using @SubscribeMultiple along with a stream, make sure that messages received on all topics follow same format or a message adapter is added for handling different format.