CODEWITHSUNDEEP
flutterdartmqtt
Diriector_Doc
Diriector_Doc

Reputation: 610

A value of type 'MqttMessage' can't be assigned to a variable of type 'MqttPublishMessage'

Every example I see is nearly identical to the code below. For some reason, this does not work form me. The problem is when I try to assign final MqttPublishMessage message, it is saying that c[0].payload is of type 'MqttMessage' which cannot be assigned to a variable of type 'MqttPublishMessage'.

MqttServerClient client = new MqttServerClient(serverUri, clientId);

client.updates.listen((List<MqttReceivedMessage<MqttMessage>> c){
    final MqttPublishMessage message = c[0].payload; // Cannot assign type
    final payload = MqttPublishPayload.bytesToStringAsString(message.payload.message);

    print('Received message:$payload from topic: ${c[0].topic}>');
});

I've tried casting which also doesn't work. I've copied the code exactly and nothing seemed to work. What is going on?

Upvotes: 2

Views: 1127

Answers (1)

L. Gangemi
L. Gangemi

Reputation: 3300

That's the full example provided here

client.updates!.listen((List<MqttReceivedMessage<MqttMessage?>>? c) {
    final recMess = c![0].payload as MqttPublishMessage;
    final pt =
        MqttPublishPayload.bytesToStringAsString(recMess.payload.message!);

    /// The above may seem a little convoluted for users only interested in the
    /// payload, some users however may be interested in the received publish message,
    /// lets not constrain ourselves yet until the package has been in the wild
    /// for a while.
    /// The payload is a byte buffer, this will be specific to the topic
    print(
        'EXAMPLE::Change notification:: topic is <${c[0].topic}>, payload is <-- $pt -->');
    print('');
  });

As you can see he's creating the variable without the type, and he's doing a recast:

final recMess = c![0].payload as MqttPublishMessage;

If this doesn't works, I would look for some errors in the client setup or maybe the data you are receiveing is not exactly what you are expecting to receive.

Upvotes: 3

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