当 UITextfield 为空时禁用所有 UIResponderStandardEditActions

Question

我目前正试图阻止所有UIResponderStandardEditActions（如copy、paste、delete）在UITextfield 为空时出现。我只想在用户输入消息时向他们展示。我已经尝试了 2 种解决方案，但目前不起作用，我不确定它是否与 iOS 12 或有关。我在UITextfield extension 中尝试了overriding 和canPerformAction 方法，并在Storyboard 中使用了后来分配给UITextfield 的自定义类，但没有运气。有没有另一种方法可以做到这一点。这是我尝试过的。

extension UITextField {
    open override func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
            if self.text!.isEmpty {
                return false
            }

            return action == #selector(UIResponderStandardEditActions.paste(_:))
        }
}

class CustomTextField: UITextField {
    override func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
        if action == #selector(UIResponderStandardEditActions.paste(_:)) || action == #selector(UIResponderStandardEditActions.copy(_:)) || action == #selector(UIResponderStandardEditActions.delete(_:)) {
            return false
        }
        return true
    }
}

Answer 1

只需用您的子类覆盖并使用此类而不是 UITextField。顺便说一句，这将禁用复制粘贴、剪切整个条件，因此您需要在开关盒中添加一些hasText: Bool 或相关条件。

@IBDesignable
class ActionsDisabledUITextField: UITextField {

    @IBInspectable var isPasteEnabled: Bool = false

    @IBInspectable var isSelectEnabled: Bool = false

    @IBInspectable var isSelectAllEnabled: Bool = false

    @IBInspectable var isCopyEnabled: Bool = false

    @IBInspectable var isCutEnabled: Bool = false

    @IBInspectable var isDeleteEnabled: Bool = false

    override func canPerformAction(_ action: Selector, withSender sender: Any?) -> Bool {
        switch action {
        case #selector(UIResponderStandardEditActions.paste(_:)) where !isPasteEnabled,
             #selector(UIResponderStandardEditActions.select(_:)) where !isSelectEnabled,
             #selector(UIResponderStandardEditActions.selectAll(_:)) where !isSelectAllEnabled,
             #selector(UIResponderStandardEditActions.copy(_:)) where !isCopyEnabled,
             #selector(UIResponderStandardEditActions.cut(_:)) where !isCutEnabled,
             #selector(UIResponderStandardEditActions.delete(_:)) where !isDeleteEnabled:
            return false
        default:
            //return true : this is not correct
            return super.canPerformAction(action, withSender: sender)
        }
    }
}