ios - [UIButton copyWithZone :]: unrecognized selector sent to instance

Question

    func createRowOfButtons(buttonTitles: [NSString]) -> UIView {
    var buttons = [UIButton]()
    let keyboardRowView = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 50))
    var dict = [UIButton:String]()
    for buttonTitle in buttonTitles 
    {
       let button = createButtonWithTitle(title: buttonTitle as String)
        buttons.append(button)
        keyboardRowView.addSubview(button)
        dict.updateValue("\(buttonTitle)", forKey: button)
    }
    allButtons = NSMutableDictionary(dictionary: dict)
    //error:[UIButton copyWithZone:]: unrecognized selector sent to instance 0x7e011bc0
    addIndividualButtonConstraints(buttons: buttons, mainView:keyboardRowView)
    return keyboardRowView
}

我是 iOS 的新手，我想创建一个 UIButton 的 NSMutableDictionary 但它给出了以下错误:

Cannot cast 'UIButton' to 'NSCopying'.

我不明白为什么会出现这个错误。

提前致谢。

Answer 1

UIButton 不符合 NSCopying protocol 因此您不能将其用作 NSDictionary 中的键

来自 Apple 文档:

The key is copied (using copyWithZone:; keys must conform to the NSCopying protocol).

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