初学iOS-HelloWorld

看图

下面附上代码import UIKit

class ViewController: UIViewController {

@IBOutlet weak var display: UITextField!

@IBAction func xianshi(_ sender: UIButton) {
    display.text="HelloWorld"
}

@IBAction func qingkong(_ sender: UIButton) {
    display.text=" "
}

}
最后看模拟器效果图