在UITextField中获取有理文本

import UIKit

let textField = UITextField(frame: CGRect(x: 50, y: 50, width: 200, height: 40))

textField.textColor = UIColor.black
textField.font = UIFont.systemFont(ofSize: 16)
textField.textAlignment = NSTextAlignment.center

class ViewController: UIViewController, UITextFieldDelegate {
    // ...
}

textField.delegate = self

func textFieldDidBeginEditing(_ textField: UITextField) {
    print("开始编辑")
}

func textFieldDidEndEditing(_ textField: UITextField) {
    print("结束编辑")
}

view.addSubview(textField)

let text = textField.text

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let textField = UITextField(frame: CGRect(x: 50, y: 50, width: 200, height: 40))
        textField.textColor = UIColor.black
        textField.font = UIFont.systemFont(ofSize: 16)
        textField.textAlignment = NSTextAlignment.center
        textField.delegate = self
        view.addSubview(textField)
    }

    func textFieldDidBeginEditing(_ textField: UITextField) {
        print("开始编辑")
    }

    func textFieldDidEndEditing(_ textField: UITextField) {
        print("结束编辑")
    }

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}