DartFlutter 泛型：类型 '(SearchFilterItemModel) => String' 不是类型 '(SearchFilterItemModel) => String' 的子类型

我已经为我的搜索筛选器项目定义了如下模型:

typedef OnFilterButtonPressed<T> = String Function(SearchFilterItemModel<T> searchFilterItem);

class SearchFilterItemModel<T> {
  final String id, name;
  final OnFilterButtonPressed<T> onPressed;

  SearchFilterItemModel({
    required this.id,
    required this.name,
    required this.onPressed,
  });
}

然后，我定义了一个筛选项列表.

List<SearchFilterItemModel> searchFilterItems = [
  SearchFilterItemModel<DateTime>(
    id: "filter_id_date",
    name: "Date",
    onPressed: (SearchFilterItemModel<DateTime> item) {
      return item.id;
    },
  ),
  SearchFilterItemModel<String>(
    id: "filter_id_cost",
    name: "Cost",
    onPressed: (SearchFilterItemModel<String> item) {
      return item.id;
    },
  ),
];

我将搜索筛选器项作为onPressed函数参数传递，因为我需要访问onPressed函数当前所在的当前模型.您可以看到，我已经在onPressed功能块中使用了项ID.

现在，我已经定义了示例Main函数，如下所示:

void main() {
  print(searchFilterItems.map<String>((SearchFilterItemModel filterItem) {
    return filterItem.onPressed(filterItem);
  }));
}

它会抛出以下错误:

未处理的异常: 类型‘(SearchFilterItemModel&lt；DateTime&gt；)=&gt；字符串’不是类型‘(SearchFilterItemModel&lt；动态&>)=&gt；字符串’的子类型

错误在Main函数的第return filterItem.onPressed(filterItem);行抛出.

问题:

1. 为什么它不能将动态类型转换为字符串类型？
2. 我如何修改我的代码来解决它？