在 flutter 中解析 json api 时在空值上使用的空检查运算符

Question

下面这两个 api 几乎相同，但一个有变体和属性，而另一个没有。所以我为 api 1 创建了 api 模型，并尝试解析两者。但只有第一个 api 有效，第二个 api returns 错误。并且错误是在空值上使用了空检查运算符。谁能帮帮我？？

这是我的 api 型号：

// To parse this JSON data, do

//     final newSingleProductModel = newSingleProductModelFromJson(jsonString);

import 'package:meta/meta.dart';
import 'dart:convert';

NewSingleProductModel newSingleProductModelFromJson(String str) =>
    NewSingleProductModel.fromJson(json.decode(str));

String newSingleProductModelToJson(NewSingleProductModel data) =>
    json.encode(data.toJson());

class NewSingleProductModel {
  NewSingleProductModel({
    required this.product,
  });

  Product product;

  factory NewSingleProductModel.fromJson(Map<String, dynamic> json) =>
      NewSingleProductModel(
        product: Product.fromJson(json["product"]),
      );

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

class Product {
  Product({
    required this.id,
    required this.name,
    required this.merchantId,
    required this.categoryId,
    required this.subCategoryId,
    required this.brandId,
    required this.subSubCategoryId,
    required this.productCode,
    required this.shopSku,
    required this.slug,
    required this.stock,
    required this.salePrice,
    required this.discount,
    required this.price,
    required this.alertQuantity,
    required this.purchasePrice,
    required this.status,
    required this.productPlacement,
    required this.productPosition,
    required this.campaignId,
    required this.details,
    required this.thumnail,
    required this.discountType,
    required this.createdAt,
    required this.updatedAt,
    required this.productImage,
    required this.productAttribute,
    required this.productVariant,
  });

  int id;
  String name;
  int merchantId;
  int categoryId;
  int subCategoryId;
  dynamic brandId;
  dynamic subSubCategoryId;
  int productCode;
  dynamic shopSku;
  String slug;
  int stock;
  String salePrice;
  int discount;
  String price;
  int alertQuantity;
  String purchasePrice;
  String status;
  int productPlacement;
  int productPosition;
  dynamic campaignId;
  String details;
  String thumnail;
  String discountType;
  DateTime createdAt;
  DateTime updatedAt;
  List<ProductImage> productImage;
  ProductAttribute productAttribute;
  List<ProductVariant> productVariant;

  factory Product.fromJson(Map<String, dynamic> json) => Product(
        id: json["id"],
        name: json["name"],
        merchantId: json["merchant_id"],
        categoryId: json["category_id"],
        subCategoryId: json["sub_category_id"],
        brandId: json["brand_id"],
        subSubCategoryId: json["sub_sub_category_id"],
        productCode: json["product_code"],
        shopSku: json["shop_sku"],
        slug: json["slug"],
        stock: json["stock"],
        salePrice: json["sale_price"],
        discount: json["discount"],
        price: json["price"],
        alertQuantity: json["alert_quantity"],
        purchasePrice: json["purchase_price"],
        status: json["status"],
        productPlacement: json["product_placement"],
        productPosition: json["product_position"],
        campaignId: json["campaign_id"],
        details: json["details"],
        thumnail: json["thumnail"],
        discountType: json["discount_type"],
        createdAt: DateTime.parse(json["created_at"]),
        updatedAt: DateTime.parse(json["updated_at"]),
        productImage: List<ProductImage>.from(
            json["product_image"].map((x) => ProductImage.fromJson(x))),
        productAttribute: ProductAttribute.fromJson(json["product_attribute"]),
        productVariant: List<ProductVariant>.from(
            json["product_variant"].map((x) => ProductVariant.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "merchant_id": merchantId,
        "category_id": categoryId,
        "sub_category_id": subCategoryId,
        "brand_id": brandId,
        "sub_sub_category_id": subSubCategoryId,
        "product_code": productCode,
        "shop_sku": shopSku,
        "slug": slug,
        "stock": stock,
        "sale_price": salePrice,
        "discount": discount,
        "price": price,
        "alert_quantity": alertQuantity,
        "purchase_price": purchasePrice,
        "status": status,
        "product_placement": productPlacement,
        "product_position": productPosition,
        "campaign_id": campaignId,
        "details": details,
        "thumnail": thumnail,
        "discount_type": discountType,
        "created_at": createdAt.toIso8601String(),
        "updated_at": updatedAt.toIso8601String(),
        "product_image":
            List<dynamic>.from(productImage.map((x) => x.toJson())),
        "product_attribute": productAttribute.toJson(),
        "product_variant":
            List<dynamic>.from(productVariant.map((x) => x.toJson())),
      };
}

class ProductAttribute {
  ProductAttribute({
    required this.id,
    required this.productId,
    required this.attributeId,
    required this.createdAt,
    required this.updatedAt,
    required this.attribute,
  });

  int id;
  int productId;
  int attributeId;
  DateTime createdAt;
  DateTime updatedAt;
  Attribute attribute;

  factory ProductAttribute.fromJson(Map<String, dynamic> json) =>
      ProductAttribute(
        id: json["id"],
        productId: json["product_id"],
        attributeId: json["attribute_id"],
        createdAt: DateTime.parse(json["created_at"]),
        updatedAt: DateTime.parse(json["updated_at"]),
        attribute: Attribute.fromJson(json["attribute"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "product_id": productId,
        "attribute_id": attributeId,
        "created_at": createdAt.toIso8601String(),
        "updated_at": updatedAt.toIso8601String(),
        "attribute": attribute.toJson(),
      };
}

class Attribute {
  Attribute({
    required this.id,
    required this.name,
    required this.status,
    required this.createdAt,
    required this.updatedAt,
    required this.attributeId,
  });

  int id;
  String name;
  int status;
  DateTime createdAt;
  DateTime updatedAt;
  int? attributeId;

  factory Attribute.fromJson(Map<String, dynamic> json) => Attribute(
        id: json["id"],
        name: json["name"],
        status: json["status"],
        createdAt: DateTime.parse(json["created_at"]),
        updatedAt: DateTime.parse(json["updated_at"]),
        attributeId: json["attribute_id"] == null ? null : json["attribute_id"],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "status": status,
        "created_at": createdAt.toIso8601String(),
        "updated_at": updatedAt.toIso8601String(),
        "attribute_id": attributeId == null ? null : attributeId,
      };
}

class ProductImage {
  ProductImage({
    required this.id,
    required this.productId,
    required this.productImage,
    required this.createdAt,
    required this.prefixUrl,
    required this.updatedAt,
  });

  int id;
  int productId;
  String productImage;
  DateTime createdAt;
  String prefixUrl;
  DateTime updatedAt;

  factory ProductImage.fromJson(Map<String, dynamic> json) => ProductImage(
        id: json["id"],
        productId: json["product_id"],
        productImage: json["product_image"],
        createdAt: DateTime.parse(json["created_at"]),
        prefixUrl: json["prefix_url"],
        updatedAt: DateTime.parse(json["updated_at"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "product_id": productId,
        "product_image": productImage,
        "created_at": createdAt.toIso8601String(),
        "prefix_url": prefixUrl,
        "updated_at": updatedAt.toIso8601String(),
      };
}

class ProductVariant {
  ProductVariant({
    required this.id,
    required this.productId,
    required this.variantId,
    required this.createdAt,
    required this.updatedAt,
    required this.variant,
  });

  int id;
  int productId;
  int variantId;
  DateTime createdAt;
  DateTime updatedAt;
  Attribute variant;

  factory ProductVariant.fromJson(Map<String, dynamic> json) => ProductVariant(
        id: json["id"],
        productId: json["product_id"],
        variantId: json["variant_id"],
        createdAt: DateTime.parse(json["created_at"]),
        updatedAt: DateTime.parse(json["updated_at"]),
        variant: Attribute.fromJson(json["variant"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "product_id": productId,
        "variant_id": variantId,
        "created_at": createdAt.toIso8601String(),
        "updated_at": updatedAt.toIso8601String(),
        "variant": variant.toJson(),
      };
}

Answer 1

试试这个：

class Model {
  Product? product;

  Model({this.product});

  Model.fromJson(Map<String, dynamic> json) {
    product =
        json['product'] != null ? new Product.fromJson(json['product']) : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.product != null) {
      data['product'] = this.product!.toJson();
    }
    return data;
  }
}

class Product {
  int? id;
  String? name;
  int? merchantId;
  int? categoryId;
  int? subCategoryId;
  Null? brandId;
  Null? subSubCategoryId;
  int? productCode;
  Null? shopSku;
  String? slug;
  int? stock;
  String? salePrice;
  int? discount;
  String? price;
  int? alertQuantity;
  String? purchasePrice;
  String? status;
  int? productPlacement;
  int? productPosition;
  Null? campaignId;
  String? details;
  String? thumnail;
  String? discountType;
  String? createdAt;
  String? updatedAt;
  List<ProductImage>? productImage;
  ProductAttribute? productAttribute;
  List<ProductVariant>? productVariant;

  Product(
      {this.id,
      this.name,
      this.merchantId,
      this.categoryId,
      this.subCategoryId,
      this.brandId,
      this.subSubCategoryId,
      this.productCode,
      this.shopSku,
      this.slug,
      this.stock,
      this.salePrice,
      this.discount,
      this.price,
      this.alertQuantity,
      this.purchasePrice,
      this.status,
      this.productPlacement,
      this.productPosition,
      this.campaignId,
      this.details,
      this.thumnail,
      this.discountType,
      this.createdAt,
      this.updatedAt,
      this.productImage,
      this.productAttribute,
      this.productVariant});

  Product.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    merchantId = json['merchant_id'];
    categoryId = json['category_id'];
    subCategoryId = json['sub_category_id'];
    brandId = json['brand_id'];
    subSubCategoryId = json['sub_sub_category_id'];
    productCode = json['product_code'];
    shopSku = json['shop_sku'];
    slug = json['slug'];
    stock = json['stock'];
    salePrice = json['sale_price'];
    discount = json['discount'];
    price = json['price'];
    alertQuantity = json['alert_quantity'];
    purchasePrice = json['purchase_price'];
    status = json['status'];
    productPlacement = json['product_placement'];
    productPosition = json['product_position'];
    campaignId = json['campaign_id'];
    details = json['details'];
    thumnail = json['thumnail'];
    discountType = json['discount_type'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    if (json['product_image'] != null) {
      productImage = <ProductImage>[];
      json['product_image'].forEach((v) {
        productImage!.add(new ProductImage.fromJson(v));
      });
    }
    productAttribute = json['product_attribute'] != null
        ? new ProductAttribute.fromJson(json['product_attribute'])
        : null;
    if (json['product_variant'] != null) {
      productVariant = <ProductVariant>[];
      json['product_variant'].forEach((v) {
        productVariant!.add(new ProductVariant.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['merchant_id'] = this.merchantId;
    data['category_id'] = this.categoryId;
    data['sub_category_id'] = this.subCategoryId;
    data['brand_id'] = this.brandId;
    data['sub_sub_category_id'] = this.subSubCategoryId;
    data['product_code'] = this.productCode;
    data['shop_sku'] = this.shopSku;
    data['slug'] = this.slug;
    data['stock'] = this.stock;
    data['sale_price'] = this.salePrice;
    data['discount'] = this.discount;
    data['price'] = this.price;
    data['alert_quantity'] = this.alertQuantity;
    data['purchase_price'] = this.purchasePrice;
    data['status'] = this.status;
    data['product_placement'] = this.productPlacement;
    data['product_position'] = this.productPosition;
    data['campaign_id'] = this.campaignId;
    data['details'] = this.details;
    data['thumnail'] = this.thumnail;
    data['discount_type'] = this.discountType;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.productImage != null) {
      data['product_image'] =
          this.productImage!.map((v) => v.toJson()).toList();
    }
    if (this.productAttribute != null) {
      data['product_attribute'] = this.productAttribute!.toJson();
    }
    if (this.productVariant != null) {
      data['product_variant'] =
          this.productVariant!.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class ProductImage {
  int? id;
  int? productId;
  String? productImage;
  String? createdAt;
  String? prefixUrl;
  String? updatedAt;

  ProductImage(
      {this.id,
      this.productId,
      this.productImage,
      this.createdAt,
      this.prefixUrl,
      this.updatedAt});

  ProductImage.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    productId = json['product_id'];
    productImage = json['product_image'];
    createdAt = json['created_at'];
    prefixUrl = json['prefix_url'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['product_id'] = this.productId;
    data['product_image'] = this.productImage;
    data['created_at'] = this.createdAt;
    data['prefix_url'] = this.prefixUrl;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}

class ProductAttribute {
  int? id;
  int? productId;
  int? attributeId;
  String? createdAt;
  String? updatedAt;
  Attribute? attribute;

  ProductAttribute(
      {this.id,
      this.productId,
      this.attributeId,
      this.createdAt,
      this.updatedAt,
      this.attribute});

  ProductAttribute.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    productId = json['product_id'];
    attributeId = json['attribute_id'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    attribute = json['attribute'] != null
        ? new Attribute.fromJson(json['attribute'])
        : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['product_id'] = this.productId;
    data['attribute_id'] = this.attributeId;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.attribute != null) {
      data['attribute'] = this.attribute!.toJson();
    }
    return data;
  }
}

class Attribute {
  int? id;
  String? name;
  int? status;
  String? createdAt;
  String? updatedAt;

  Attribute({this.id, this.name, this.status, this.createdAt, this.updatedAt});

  Attribute.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    status = json['status'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['status'] = this.status;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}

class ProductVariant {
  int? id;
  int? productId;
  int? variantId;
  String? createdAt;
  String? updatedAt;
  Variant? variant;

  ProductVariant(
      {this.id,
      this.productId,
      this.variantId,
      this.createdAt,
      this.updatedAt,
      this.variant});

  ProductVariant.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    productId = json['product_id'];
    variantId = json['variant_id'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    variant =
        json['variant'] != null ? new Variant.fromJson(json['variant']) : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['product_id'] = this.productId;
    data['variant_id'] = this.variantId;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.variant != null) {
      data['variant'] = this.variant!.toJson();
    }
    return data;
  }
}

class Variant {
  int? id;
  String? name;
  int? attributeId;
  int? status;
  String? createdAt;
  String? updatedAt;

  Variant(
      {this.id,
      this.name,
      this.attributeId,
      this.status,
      this.createdAt,
      this.updatedAt});

  Variant.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    attributeId = json['attribute_id'];
    status = json['status'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['attribute_id'] = this.attributeId;
    data['status'] = this.status;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}

在 flutter 中解析 json api 时在空值上使用的空检查运算符

Null check operator used on a null value while parsing json api in flutter

api

flutter

flutter-http