不能将参数类型“List<Categories>”分配给参数类型“Iterable<Categories>”

Question

下面是我的模型类类别

List<Categories> categoriesFromJson(String str) => List<Categories>.from(json.decode(str).map((x) => Categories.fromJson(x)));

String categoriesToJson(List<Categories> data) => json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class Categories {
  Categories({
    this.id,
    this.name,
    this.parentId,
    this.slug,
    this.position,
    this.status,
  });

  int id;
  String name;
  int parentId;
  String slug;
  int position;
  int status;

  factory Categories.fromJson(Map<String, dynamic> json) => Categories(
    id: json["id"],
    name: json["name"],
    parentId: json["parent_id"],
    slug: json["slug"],
    position: json["position"],
    status: json["status"],
  );

  Map<String, dynamic> toJson() => {
    "id": id,
    "name": name,
    "parent_id": parentId,
    "slug": slug,
    "position": position,
    "status": status,
  };
}

我的apiServices

static Future<List<Categories>> fetchCategories() async {
String url = "/categories/all";
var response = await http.get(BASE_URL + url);
if(response.statusCode == 200) {
return categoriesFromJson(response.body).toList();
} else {
return null;
}
}

我的控制器中的api调用函数

var categoryNames = <Categories>[].obs;
void fetchCategories() async {
    try{
      isLoading(true);

      var res = await ApiServices.fetchCategories();
      if(res !=null){
        categoryNames.addAll(res);
      }
    }finally{
      isLoading(false);
    }
  }

在控制器中，当categoryNames.addAll中的res (Res)下划线为红色时，会显示以上错误信息。当我对apiService的categoryNews和fetchCategories()使用相同的类型时，为什么会出现这个错误。任何帮助都将不胜感激。

​

Answer 1

尝试像这样显式地定义类型

List<Categories> categoryNames = [];

还要确保从.map()返回一个列表并将.toList()添加到末尾