如何修复 flutter 中的 "type 'String' is not a subtype of type '(String?) => String?" 错误

Question

我正在学习 flutter 并且遇到了很多关于 flutter 的错误...

我正在尝试使用以下方法验证文本字段：

validateName() {
String value = '';
if (value.isEmpty) return 'Username is Required.';
final RegExp nameExp = new RegExp(r'^[A-za-zğüşöçİĞÜŞÖÇ ]+$');
if (!nameExp.hasMatch(value))
  return 'Please enter only alphabetical characters.';
return value;
}

但是，我在 textformbuilder 的 validationFunction 上遇到上述错误：

TextFormBuilder(
        enabled: !viewModel.loading,
        prefix: Feather.user,
        hintText: "Username",
        textInputAction: TextInputAction.next,
        validateFunction: validateName(),
        onSaved: (String val) {
          viewModel.setName(val);
        },
        focusNode: viewModel.usernameFN,
        nextFocusNode: viewModel.emailFN,
      ),

提前致谢！

Answer 1

验证函数与您的函数不同...因此更改函数验证名称

  String validateName(String? value) {
   if (value!.isEmpty) return 'Username is Required.';
   final RegExp nameExp = new RegExp(r'^[A-za-zğüşöçİĞÜŞÖÇ ]+$');
   if (!nameExp.hasMatch(value))
   return 'Please enter only alphabetical characters.';
   return value;
  }

在文本字段构建器上...像这样放置 validateFunction

TextFormBuilder(
 validateFunction: validateName,
)

如何修复 flutter 中的 "type 'String' is not a subtype of type '(String?) => String?" 错误

How to fix "type 'String' is not a subtype of type '(String?) => String?" error in flutter

string

typeerror

flutter