First program in Swift - HelloWorld - ios

Question

I have some issue with my first code in Swift, when I'm running it, it seems fine, but it shows e.g. Hello Optional "(name)" instead of Hello (name).
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var helloLabel: UILabel!
#IBOutlet weak var nameTextField: UITextField!
#IBOutlet weak var sayHelloButton: UIButton!
#IBAction func sayHelloAction(sender: AnyObject)
{
let name = nameTextField.text
if name!.isEmpty {
let alert = UIAlertController(title: "Error", message: "Please enter a name", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
} else {
helloLabel.text = "Hello \(name)!"
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
setupUI()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func setupUI() {
helloLabel.text = "Hello There!"
helloLabel.textColor = UIColor.blueColor()
helloLabel.textAlignment = NSTextAlignment.Center
nameTextField.placeholder = "Enter your name"
sayHelloButton.setTitle("Say Hello", forState: .Normal)
}
}
Can anyone help me, please?
Doms.

Answer 1

In Swift you have a type called Optional. This is used to express nullability. You need to do what is called unwraping the optional. I will discourage you from force unwrapping ! it will cause your app to crash. You can unwrap an optional value using the if let statement:
#IBAction func sayHelloAction(sender: AnyObject) {
if let name = nameTextField.text where !name.isEmpty {
helloLabel.text = "Hello \(name)"
} else {
let alert = UIAlertController(title: "Error", message: "Please enter a name", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
}

Answer 2

I ran into this when I was just learning Swift myself, and it tends to pop out in all sorts of places. For instance, I couldn't understand why one of my tableview columns always said "0" instead of "1" or "2". It was in fact saying "O"ptional!
The simplest solution is to guard everything everywhere. That way the compiler knows you've checked that it's not nil, and "unwraps" the value for you. so instead of:
let name = nameTextField.text
just do a:
guard let name = nameTextField.text else { return }
Replace that return with something more appropriate. From that point on, name is the string and won't have the Optional(theThingYouReallyWanted) any more.
note: as I said at the start, this has a habit of showing up in weird places. If you bind Optionals into things like text fields or table columns, you'll see it when you don't expect it. I strongly suggest making getter/setter properties for all UI work, and using the guard to unwrap as above and instead of return hand back an empty string or something similar.

Answer 3

You get the Optional("") because the optional value is not unwrapped. You need to put a ! after the object and you won't get the Optional("") bit any more. I would show you the code but you haven't shown us the print() statement. I made some sample ones below that I think would replicate the problem, though I haven't tried them.
var value:String?
value = "Hello, World"
print("The Value Is \(value)") // Prints "The Value Is Optional(Hello, World)"
print("The Value Is \(value!)")// Prints "The Value Is Hello, World"