NoSuchMethodError: метод '[]' был вызван с нулевым значением - PullRequest
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NoSuchMethodError: метод '[]' был вызван с нулевым значением

0 голосов
/ 07 февраля 2020

Я новичок, чтобы трепетать. Я пытаюсь получить json от API из следующего кода: 

final response = await http.get(url, headers: {
        'Content-Type': 'application/json; charset=utf-8',
      });
      print((json.decode(response.body)['categories'] as List)
          .map((data) => CategoryModel.fromJson(data))
          .toList());
      final responseJson = (json.decode(response.body)['categories'] as List)
          .map((data) => CategoryModel.fromJson(data))
          .toList();
      return responseJson;

Однако я не могу десериализовать его. Вот ошибка, которую я получаю: 

I/flutter (19749): NoSuchMethodError: The method '[]' was called on null.
I/flutter (19749): Receiver: null
I/flutter (19749): Tried calling: []("products")

CategoryModel: 

import 'package:pbl_store/models/cat_assoc.dart';

class CategoryModel{
  String id;
  String relationShipId;
  String name;
  String idParent;
  String levelDept;
  String numberProductRecursive;
  String active;
  CatAsso associationModel;

  CategoryModel({this.id, this.name, this.idParent, this.relationShipId,
    this.levelDept, this.associationModel, this.numberProductRecursive, this.active});

  factory CategoryModel.fromJson(Map<String, dynamic> parsedJson) {

    return CategoryModel(
      id: parsedJson['id'].toString(),
      name: parsedJson['name'] ,
      idParent: parsedJson['id_parent'],
      levelDept: parsedJson['level_depth'],
      active: parsedJson['active'],
      numberProductRecursive: parsedJson['nb_products_recursive'].toString(),
      associationModel: CatAsso.fromJson(parsedJson['associations'])
    );
  }

}

ProductInCategory: 

class ProductInCategory{
  String id;

  ProductInCategory({this.id});

  factory ProductInCategory.fromJson(Map<String, dynamic> parsedJson){
    return ProductInCategory(
        id: parsedJson['id'].toString()
    );
  }
}

CatAsso: 

import 'package:pbl_store/models/product_in_category.dart';

class CatAsso{
  List<ProductInCategory> filterPs;

  CatAsso({this.filterPs});
  factory CatAsso.fromJson(Map<String, dynamic> parsedJson) {
    var product = parsedJson['products'];
    List<ProductInCategory> filteredProductList = List();

    if(product != null){
      filteredProductList = List<ProductInCategory>.from(product.map<ProductInCategory>((i) => ProductInCategory.fromJson(i)));
    }
    return CatAsso(
        filterPs: filteredProductList
    );
  }
}

Внутри каждой категории есть идентификатор подкатегории и идентификатор продукта. Я хочу идентификатор продукта. вот json я пытаюсь получить: 

{
    "categories": [
        {
            "id": 2,
            "id_parent": "1",
            "level_depth": "1",
            "nb_products_recursive": "162",
            "active": "1",
            "id_shop_default": "1",
            "is_root_category": "1",
            "position": "0",
            "date_add": "2018-12-31 09:52:57",
            "date_upd": "2018-12-31 09:52:57",
            "name": "Home",
            "link_rewrite": "home",
            "description": "",
            "meta_title": "",
            "meta_description": "",
            "meta_keywords": "",
            "associations": {
                "categories": [
                    {
                        "id": "3"
                    },
                    {
                        "id": "4"
                    },
                    {
                        "id": "5"
                    }
                ],
                "products": [
                    {
                        "id": "8"
                    },
                    {
                        "id": "13"
                    },
                    {
                        "id": "14"
                    },
                    {
                        "id": "17"
                    },
                    {
                        "id": "18"
                    },
                    {
                        "id": "19"
                    },
                    {
                        "id": "125"
                    },
                    {
                        "id": "126"
                    },
                    {
                        "id": "127"
                    },
                    {
                        "id": "128"
                    },
                    {
                        "id": "129"
                    },
                    {
                        "id": "130"
                    },
                    {
                        "id": "131"
                    },
                    {
                        "id": "132"
                    },
                    {
                        "id": "133"
                    },
                    {
                        "id": "134"
                    },
                    {
                        "id": "135"
                    },
                    {
                        "id": "136"
                    },
                    {
                        "id": "137"
                    },
                    {
                        "id": "138"
                    },
                    {
                        "id": "139"
                    },
                    {
                        "id": "140"
                    },
                    {
                        "id": "141"
                    },
                    {
                        "id": "142"
                    },
                    {
                        "id": "143"
                    },
                    {
                        "id": "145"
                    },
                    {
                        "id": "146"
                    },
                    {
                        "id": "147"
                    },
                    {
                        "id": "148"
                    },
                    {
                        "id": "149"
                    },
                    {
                        "id": "150"
                    },
                    {
                        "id": "151"
                    },
                    {
                        "id": "152"
                    },
                    {
                        "id": "153"
                    },
                    {
                        "id": "154"
                    },
                    {
                        "id": "156"
                    },
                    {
                        "id": "157"
                    },
                    {
                        "id": "158"
                    },
                    {
                        "id": "159"
                    },
                    {
                        "id": "160"
                    },
                    {
                        "id": "161"
                    },
                    {
                        "id": "162"
                    },
                    {
                        "id": "163"
                    },
                    {
                        "id": "164"
                    },
                    {
                        "id": "165"
                    },
                    {
                        "id": "166"
                    },
                    {
                        "id": "167"
                    },
                    {
                        "id": "168"
                    },
                    {
                        "id": "169"
                    },
                    {
                        "id": "170"
                    },
                    {
                        "id": "171"
                    },
                    {
                        "id": "172"
                    },
                    {
                        "id": "173"
                    },
                    {
                        "id": "174"
                    },
                    {
                        "id": "175"
                    },
                    {
                        "id": "178"
                    },
                    {
                        "id": "179"
                    },
                    {
                        "id": "180"
                    },
                    {
                        "id": "181"
                    },
                    {
                        "id": "182"
                    },
                    {
                        "id": "183"
                    },
                    {
                        "id": "184"
                    },
                    {
                        "id": "185"
                    },
                    {
                        "id": "186"
                    },
                    {
                        "id": "187"
                    },
                    {
                        "id": "188"
                    },
                    {
                        "id": "189"
                    },
                    {
                        "id": "190"
                    },
                    {
                        "id": "191"
                    },
                    {
                        "id": "192"
                    },
                    {
                        "id": "193"
                    },
                    {
                        "id": "195"
                    }
                ]
            }
        }

    ]
}

Пожалуйста, объясните мне, почему возникает эта проблема, и помогите мне найти решение ....

1 Ответ

0 голосов
/ 07 февраля 2020

Попробуйте это 

Future <CategoryModel> getCategories() async {
  try {

    final response = await http.get(url ,
      headers: {
         'Content-Type': 'application/json; charset=utf-8',
      },
    );
    ////print(response.body);
    return categoryModelFromJson(response.body);
  }on Exception catch (e){
    print(e);
    CategoryModel reply=CategoryModel();
    return reply;
  }
}

======== 

    // To parse this JSON data, do
//
//     final categoryModel = categoryModelFromJson(jsonString);

import 'dart:convert';

CategoryModel categoryModelFromJson(String str) => CategoryModel.fromJson(json.decode(str));

String categoryModelToJson(CategoryModel data) => json.encode(data.toJson());

class CategoryModel {
    List<CategoryModelCategory> categories;

    CategoryModel({
        this.categories,
    });

    factory CategoryModel.fromJson(Map<String, dynamic> json) => CategoryModel(
        categories: List<CategoryModelCategory>.from(json["categories"].map((x) => CategoryModelCategory.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "categories": List<dynamic>.from(categories.map((x) => x.toJson())),
    };
}

class CategoryModelCategory {
    int id;
    String idParent;
    String levelDepth;
    String nbProductsRecursive;
    String active;
    String idShopDefault;
    String isRootCategory;
    String position;
    String dateAdd;
    String dateUpd;
    String name;
    String linkRewrite;
    String description;
    String metaTitle;
    String metaDescription;
    String metaKeywords;
    Associations associations;

    CategoryModelCategory({
        this.id,
        this.idParent,
        this.levelDepth,
        this.nbProductsRecursive,
        this.active,
        this.idShopDefault,
        this.isRootCategory,
        this.position,
        this.dateAdd,
        this.dateUpd,
        this.name,
        this.linkRewrite,
        this.description,
        this.metaTitle,
        this.metaDescription,
        this.metaKeywords,
        this.associations,
    });

    factory CategoryModelCategory.fromJson(Map<String, dynamic> json) => CategoryModelCategory(
        id: json["id"],
        idParent: json["id_parent"],
        levelDepth: json["level_depth"],
        nbProductsRecursive: json["nb_products_recursive"],
        active: json["active"],
        idShopDefault: json["id_shop_default"],
        isRootCategory: json["is_root_category"],
        position: json["position"],
        dateAdd: json["date_add"],
        dateUpd: json["date_upd"],
        name: json["name"],
        linkRewrite: json["link_rewrite"],
        description: json["description"],
        metaTitle: json["meta_title"],
        metaDescription: json["meta_description"],
        metaKeywords: json["meta_keywords"],
        associations: Associations.fromJson(json["associations"]),
    );

    Map<String, dynamic> toJson() => {
        "id": id,
        "id_parent": idParent,
        "level_depth": levelDepth,
        "nb_products_recursive": nbProductsRecursive,
        "active": active,
        "id_shop_default": idShopDefault,
        "is_root_category": isRootCategory,
        "position": position,
        "date_add": dateAdd,
        "date_upd": dateUpd,
        "name": name,
        "link_rewrite": linkRewrite,
        "description": description,
        "meta_title": metaTitle,
        "meta_description": metaDescription,
        "meta_keywords": metaKeywords,
        "associations": associations.toJson(),
    };
}

class Associations {
    List<ProductElement> categories;
    List<ProductElement> products;

    Associations({
        this.categories,
        this.products,
    });

    factory Associations.fromJson(Map<String, dynamic> json) => Associations(
        categories: List<ProductElement>.from(json["categories"].map((x) => ProductElement.fromJson(x))),
        products: List<ProductElement>.from(json["products"].map((x) => ProductElement.fromJson(x))),
    );

    Map<String, dynamic> toJson() => {
        "categories": List<dynamic>.from(categories.map((x) => x.toJson())),
        "products": List<dynamic>.from(products.map((x) => x.toJson())),
    };
}

class ProductElement {
    String id;

    ProductElement({
        this.id,
    });

    factory ProductElement.fromJson(Map<String, dynamic> json) => ProductElement(
        id: json["id"],
    );

    Map<String, dynamic> toJson() => {
        "id": id,
    };
}
...