Question

我已按照此tutorial了解如何将textField限制为特定长度和字符集。

这是我的代码，但代理人没有被调用：

VC类：调用它（在调试时验证）

var textManager = TextManager()
@IBOutlet weak var enterName_text: UITextField!


func onVideDidLoad() {
...
    enterName_text.placeholder = StringConstans.name
    enterName_text.delegate = textManager
    }

TextManager类：

import Foundation

public class TextManager: NSObject, UITextFieldDelegate {

    public func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        if string.characters.count == 0 {
            return true
        }
         let currentText = textField.text ?? ""
        let prospectiveText = (currentText as NSString).stringByReplacingCharactersInRange(range, withString: string)


            return prospectiveText.containsOnlyCharactersIn("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz") &&
                prospectiveText.characters.count <= 6
          }
}

Answer 1

以下代码有效。你们有何不同？

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!
    let textManager = TextManager()

    override func viewDidLoad() {
        super.viewDidLoad()
        textField.delegate = textManager
    }
}

public class TextManager: NSObject, UITextFieldDelegate {

    public func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        print("should")
        if string.characters.count == 0 {
            return true
        }
        let currentText = textField.text ?? ""
        let prospectiveText = (currentText as NSString).stringByReplacingCharactersInRange(range, withString: string)

        return prospectiveText.containsOnlyCharactersIn("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz") &&
            prospectiveText.characters.count <= 6
    }
}

extension String {
    func containsOnlyCharactersIn(matchCharacters: String) -> Bool {
        let disallowedCharacterSet = NSCharacterSet(charactersInString: matchCharacters).invertedSet
        return self.rangeOfCharacterFromSet(disallowedCharacterSet) == nil
    }
}

为什么shouldChangeCharactersInRange委托方法永远不会被调用？

1 个答案: