ios - 重写 UITextField 委托(delegate)方法

Question

我正在将这个 Objective-C 项目 ( TSCurrencyTextField ) 转换为 Swift。它是一个 UITextField 子类，被格式化为接受货币值。 This是我要转换的 .m 文件。

其中，UITextField 的方法shouldChangeCharactersInRange 被TSCurrencyTextField 类型的参数覆盖。像这样(看最后一个方法)，

@interface TSCurrencyTextFieldDelegate : NSObject <UITextFieldDelegate>
@property (weak, nonatomic) id<UITextFieldDelegate> delegate;
@end

@implementation TSCurrencyTextField
{
    TSCurrencyTextFieldDelegate* _currencyTextFieldDelegate;
}

- (id) initWithFrame: (CGRect) frame
{
    self = [super initWithFrame: frame];
    if ( self )
    {
        [self TSCurrencyTextField_commonInit];
    }
    return self;
}

- (void) TSCurrencyTextField_commonInit
{
    // ...

    _currencyTextFieldDelegate = [TSCurrencyTextFieldDelegate new];
    [super setDelegate: _currencyTextFieldDelegate];
}

- (void) setDelegate:(id<UITextFieldDelegate>)delegate
{
    _currencyTextFieldDelegate.delegate = delegate;
}

- (id<UITextFieldDelegate>) delegate
{
    return _currencyTextFieldDelegate.delegate;
}

@end


@implementation TSCurrencyTextFieldDelegate

- (BOOL) textField: (TSCurrencyTextField *) textField shouldChangeCharactersInRange: (NSRange) range replacementString: (NSString *) string
{
    // ...
}

@end

这是我的 Swift 翻译。

protocol CurrencyTextFieldDelegate: NSObjectProtocol, UITextFieldDelegate {
    weak var delegate: UITextFieldDelegate? { get set }
}

public class CurrencyTextField: UITextField {

    override public var delegate: UITextFieldDelegate? {
        get {
            return self.delegate as? CurrencyTextFieldDelegate
        }
        set {
            self.delegate = newValue
        }
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }

    private func commonInit() {

    }
}

// MARK: - CurrencyTextFieldDelegate
extension CurrencyTextField: CurrencyTextFieldDelegate {
    public func textField(textField: CurrencyTextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        return false
    }
}

但是我得到以下错误。

Objective-C method 'textField:shouldChangeCharactersInRange:replacementString:' provided by method 'textField(:shouldChangeCharactersInRange:replacementString:)' conflicts with optional requirement method 'textField(:shouldChangeCharactersInRange:replacementString:)' in protocol 'UITextFieldDelegate'

如何修复此错误？

Answer 1

对于您要实现的目标，您不需要子类化 UITextFieldDelegate。

而不是在您的 init 方法中，使用适当的函数向 self 添加一个目标。

override init(frame: CGRect) {
    super.init(frame: frame)
    self.addTarget(self, action: "formatText", for: .editingChanged)
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    self.addTarget(self, action: "formatText", for: .editingChanged)
}

func formatText() {
   // Edit self.text here
}