Connecting to MQTT happens after publish due to async - ios

Question

I'm using CocoaMQTT to connect and publish events. To publish, its important that I am connected to MQTT. But connect is async and so is publish. I want it to be sequential that first it should connect and once connected then publish so for example if the connect happens after 5mins then publish should happen after that.
https://github.com/emqtt/CocoaMQTT
How exactly can I do that?
Here is my code:
class ViewController: UIViewController {
var iot: MQTTDelegate!
#IBAction func click(_ sender: Any) {
self.iot = IoT(
withClientId: "clientId",
host: "host",
port: 1883
)
iot.connect(username: "username", password: "token")
iot.publish(topic: "hello", message: "")
}
}
If I move connect to a separate button then it works as first I click the connect button and then I click the "click" button so its sequential. How do I make the above code sequential?
I used PromiseKit to promisify the code but I dont know what exactly to fulfill to connect.

Answer 1

It looks like you are trying to establish a connection to an MQTT server and publish a message to a topic, but the connection is being established after the message is published due to asynchronous behavior.
To fix this issue, you can use the connect() method of the MQTTClient class to establish the connection before publishing the message. The connect() method takes a completion block that is called when the connection is established or if an error occurs.
Here is an example of how you could modify your code to establish the connection before publishing the message:
client.connect { error in
if error == nil {
// Connection was successful
client.publish("topic", withString: "Hello, World!")
} else {
// There was an error connecting to the MQTT server
}
}
This way, the connection to the MQTT server will be established before the message is published, and the message will be sent as soon as the connection is ready.