iOS -Textfield 的 shouldChangeCharactersIn 范围正在禁用 .editingChanged 的​​目标方法

Question

我有一个文本字段，我通过设置 .autocapitalizationType = .none 禁用大写字母，在 shouldChangeCharactersIn range 中我用小写字母替换所有大写字母 通过 .

强制只使用小写字母可以正常工作，但我添加到 .editingChanged 的目标方法停止工作。

为什么 .editingChanged 停止工作？

let emailTextField: UITextField = {
    let textField = UITextField()
    return textField
}()

let userNameTextField: UITextField = {
    let textField = UITextField()
    textField.autocapitalizationType = .none
    textField.addTarget(self, action: #selector(printSomething), for: .editingChanged)
    return textField
}()

@objc func printSomething() {
    // as I type inside the usernameTextField this no longer prints
    print("something")
}

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    // only change characters for username textfield
    if textField == userNameTextField {

        userNameTextField.text = (textField.text! as NSString).replacingCharacters(in: range, with: string.lowercased())
        return false
    }
    return true
}

Answer 1

问题出在您的 userNameTextField 声明上。当你初始化它时，没有 self。您需要将其声明更改为 lazy:

lazy var userNameTextField: UITextField = {
    let textField = UITextField()
    textField.autocapitalizationType = .none
    textField.addTarget(self, action: #selector(editingChanged), for: .editingChanged)
    return textField
}()

---

我还会删除范围内的 shouldChangeCharacters 并在 editingChanged 方法中进行所有字符操作：

@objc func editingChanged(_ textField: UITextField) {
    print(textField.text!)
    textField.text = textField.text!.lowercased()
}

Answer 2

更改为 return true

   if textField == userNameTextField {

        userNameTextField.text = (textField.text! as NSString).replacingCharacters(in: range, with: string.lowercased())
        return true
    }