iOS（Swift）：UITextField是不是成为firstFirstsponder方法后的第一响应者吗？

Question

I have an array of UITextField s inside a UIViewController :

@IBOutlet weak var textField1: UITextField!
@IBOutlet weak var textField2: UITextField!
var textFields: [UITextField] {
    return [textField1, textField2]
}

In my viewDidLoad method, I set the first element of the textFields array to be the first responder and set all of their delegates as follows:

override func viewDidLoad() {
    super.viewDidLoad()

    textFields[0].becomeFirstResponder()
    textFields.forEach({ $0.delegate = self })

    print(textFields.map({ $0.isFirstResponder })) // [false, false]

}

However, the print statement in the viewDidLoad prints [false, false] rather than [true, false] as I might have expected. Why?

Thanks

Answer 1

You're running this code too soon. No text field can become first responder during viewDidLoad , because no text field is even in the interface yet.

To put it another way, try changing your code to:

print(textFields.map({ $0.window == nil }))

You'll get [true, true] , proving that the text fields are not yet in any window. But first responder status is window-based; a free-floating text field cannot be first responder.