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View not refreshed when calling UIButton.isHidden = true / false

I am using xcode 8.2

and swift

to create a simple application.

I added UIButton

to my view using Interface Builder

.

I've added the appropriate outputs for the button:

@IBOutlet weak var myBtn: UIButton!

I want this button to be hidden on startup, so in viewDidLoad

I am setting the value Hidden

. Like this:

override func viewDidLoad() {
        super.viewDidLoad() 
        ...
        myBtn.isHidden = true
        ...
        mqttConfig = MQTTConfig(clientId: "iphone7", host: "192.xx.xx.150", port: 18xx, keepAlive: 60)

        mqttConfig.onMessageCallback = { mqttMessage in
            if ( mqttMessage.topic == "status" ) {
                if ( mqttMessage.payloadString?.localizedStandardContains("show") )! {
                    self.showButton = true
                } else if ( mqttMessage.payloadString?.localizedStandardContains("hide")  )! {
                    self.showButton = false
                }
                self.showHideSeatButtons()
            } else {
                // something to do in case of other topics
            }
        }

Later in the code, I have a function to show / hide this button.

func showHideButton(){
    if ( self.showButton ) {
        print("button enabled!")
        myBtn.isHidden = false

    } else {
        print("button disabled!")
        myBtn.isHidden = true
    }
}

When I call this function (getting a specific message using MQTT), I get printouts, but I can't see the button. If I click the Where I Know button, then the button appears.

Any idea what might be going on here? I spent an hour googling it now! Please do not suggest a object-c

way to solve this problem as I do not know object-c

.

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2 answers


In the onMessageCallback block

Replace next line

self.showHideSeatButtons()


from

DispatchQueue.main.async {
    self.showHideSeatButtons()
}

Note . Changes / updates related to the user interface should be processed by the main queue (thread).

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Since you are calling a service, you may not be working on the same thread. Try the following:



func showHideButton(){
        DispatchQueue.main.async {
            if (self.showButton ) {
                print("button enabled!")
                self.myBtn.isHidden = false

            } else {
                print("button disabled!")
                self.myBtn.isHidden = true
            }
        }
    }
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