fatal error: unexpectedly found nil while unwrapping an Optional value in Swift

问题

So I'm trying to get the text of an input field in Swift. So here's what I got

class ViewController: UIViewController {

    @IBOutlet var passwordField: UITextField!
    @IBOutlet var usernameField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()            
        //Try to log user in by default
        let user = usernameField.text
        let password = passwordField.text

It all looks good (I know I didn't close the class, I just pulled it directly out) and when I go to run it, I get

fatal error: unexpectedly found nil while unwrapping an Optional value (lldb)

and

(You'll have to open the image in a new tab to see it)

I binded the input fields with the IBOutlet successful, I know that. Any ideas?

回答1:

Try this way I think this will work :

if let abc = usernameField.text{
        let user = abc

    }

回答2:

i think You Have to Check This in TextField's Delegate Method

func textFieldDidEndEditing(textField: UITextField) {

}

instead ViewDidLoad Or On Action of ButtonClick

Cause TextField Are Empty On ViewDidLoad!

回答3:

I had this problem while setting the delegate to a text field. Couldn't figure out was wrong then realized that I had declared the class for a second view controller as a view controller not a UIViewController. I'm new at this.

来源：https://stackoverflow.com/questions/26701993/fatal-error-unexpectedly-found-nil-while-unwrapping-an-optional-value-in-swift