Swift Show Alert to User

Say that I needed an alert for my app to let the user that my app has some mistakes or you i wanted to user to select some options before moving on, in cases like these you may wanna show a messageBox like alert using the UIAlertController class, let’s begin

Initialize class instance

First of all we need an object created from this class:

var alert : UIAlertController = UIAlertController(title: "Somethings happening", message: "Whadaya wanna do?", prefferredStyle: .alert)

Now my alert is ready but it does not have any interactable buttons or something, just an info text. So i want to add and Ok button:

var action = UIAlertAction(title: "Ok", style: .default, handler: { (action) in
    print("Got it!")
 })

 alert.addAction(alert)

Now we just added an Ok button. One thing that you might notice is that the 3rd paremeter of the UIAlertAction constructor method. This is a closure , a void method actually. As you can guess from the parameter name handler, we use this method to handle what will happen when the user presses this Ok button? So we do not need to name this method and we just printed a log statement in it. Also i need to say that if i would for example, call another method or would try to access a property in my class while in this closure, i gotta add self. statement before doing so, let’s make it clearer :

// here is my global space in the class
func foo() {

}


func  someFunc() {

        var action = UIAlertAction(title: "Ok", style: .default, handler: { (action) in
        
            print("Got it!")
            self.foo()

    })
}

Add another button : Cancel

Here comes my cancel button that’ll dismiss the alert :

var cancelAction =  UIAlertAction(title: "Cancel", style: .cancel, handler: { (action) in
    self.dismiss(animated: true, completion: nil)
 })

You can again see the self. statement in my handler closure method. There is also this completion: nil statement. This is another method decleraction actually, when that line of coded executed and completed successfully, the method name we sent as parameter to here, will get executed. Since we entered nil here, no method or function will be invoked after completion.

That’ll be all, thanks. Have a look at the developer apple portal it’s quite well written so you almost do not need any other source.