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After clicking on the button,nothing is changing.Before setting the constraints,button was working fine

I am trying to build a basic app in here.I set a button and label using an Interface Builder. After clicking on the button,nothing is changing.Before setting the constraints,button was working fine and other strings which I had stored in the array where displaying but after setting the constraints,clicking on the button changes nothing.

I'm assuming that you have an @IBAction that changes the label when the button is clicked. In your storyboard, when you right click (or control + left click) on the button, do you see function connected under the "Sent Events"? It would likely be tied to the "Touch up inside" event. If there is no connection, you need to reconnect the event to the function in your view controller class.