构建反应式表单时遇到运行时错误

Question

尝试使用dartdevc在Dart中构建活动的Angular表单时发生此运行时错误：

Type 'List<Type>' is not a subtype of expected type 'num'. 

错误发生在我的buildForm()函数中。

  ControlGroup buildForm()
  {
    return FormBuilder.controlGroup(
      {
        // Error happens on the next statement 
        'fee': Control<num>([null, PositiveNumValidator]),
        'fi':  Control<num>([null, PositiveNumValidator]),
        'fo':  Control<num>([null, PositiveNumValidator]),
        'fum': Control<num>([null, PositiveNumValidator])
      });
  }

如果我在Control配置中删除<num>，则错误将更改为：

Type 'List<Type>' is not a subtype of expected type 'String'.

该函数的整个上下文是：

class MyForm implements OnInit
{
  ControlGroup form;
  ...

  ControlGroup buildForm()
  {...}

  @override
  ngOnInit()
  form = buildForm();
}

任何建议将不胜感激。

Answer 1

'fee': Control<num>([null, PositiveNumValidator]),

应该

'fee': Control<num>([null, PositiveNumValidator().validate]),

要么

'fee': [null, PositiveNumValidator().validate],

也可以看看

• https://webdev.dartlang.org/api/angular_forms/angular_forms/FormBuilder-class
• https://webdev.dartlang.org/api/angular_forms/angular_forms/Validators/required
• https://webdev.dartlang.org/api/angular_components/angular_components/PositiveNumValidator/validate