没有这样的方法错误：类列表<Category>没有实例获取者'entries'接收器：可增长列表的实例(长度：5)

Question

这是我所有的代码，我认为我得到了错误，当我写得到selectedcategories函数，但我没有解决它

Widget build(BuildContext context) {
return Flexible(
child: Obx(
() => ListView.builder(
itemCount: controller.selectedCategories.length,
itemBuilder: (_, index) {
return CategoryWidget(
category: controller.selectedCategories[index],
);
},
),
),
);

var _categories = {
Category("Aksiyon", Color(0xFF21d0d0)): false,
Category("Bilimkurgu", Color(0xFF21d0d0)): false,
Category("Suç", Color(0xFF21d0d0)): false,
Category("Macera", Color(0xFF21d0d0)): false,
Category("Drama", Color(0xFF21d0d0)): false,

}.obs;

void toggle(Category item){_categories [item]= !(_categories[item]?? true};
print(_categories[item]);
}
get selectedCategories => categories.entries
.where((element) => element.value).map((e) => e.key)
.toList();
get categories => _categories.entries.map((e) => e.key).toList();}

class Category{
final String name;
final Color color;
Category(this.name,this.color);}

我找不到问题，有人能帮助我，我分享我的代码。我在等你的回答

Answer 1

你这一行打错了

void toggle(Category item){_categories [item]= !(_categories[item]?? true};
print(_categories[item]);
}
!(_categories[item]?? true};
//Change to
!(_categories[item]?? true);
//The curly brackets after the semicolon

---

更新:
这是因为你的selectedCategoriesgetter从另一个gettercategories读取getter类别返回list<Category>而不是Map<Category, bool>

get selectedCategories => categories.entries
.where((element) => element.value).map((e) => e.key)
.toList();
get categories => _categories.entries.map((e) => e.key).toList();}

要解决这个问题，只需将selectedCategories更改为读取地图

get selectedCategories => _categories.entries
//instead of 
get selectedCategories => categories.entries