未经手的异常：type＆＃x27; list＆lt; dynamic＆gt;＆＃x27;不是类型的子类型。 |如何在模型firebase中输入对象阵列

Question

我一直在尝试从Firebase获取数据 因此，实际数据是：

如何获取ImageUrl？

我的尝试是：

class ProductModel {
  String? name;
  String? price;
  String? discountPrice;
  String? discountRate;
  String? category;
  String? description;
  List<imageObject>? image;

  ProductModel(
      {required this.name,
      required this.price,
      this.category,
      this.description,
      this.discountPrice,
      this.discountRate,
      this.image});

  ProductModel.fromMap(Map<String, dynamic> data) {
    
    name = data['name'];
    // image = data['imageUrls'][0]['url']; // To get single image i do this
    image = data['imageUrls']; // but this is not working 
    category = data['category'];
    description = data['Description'];
    price = data['price'];
    discountPrice = data['discountPrice'];
    discountRate = data['discountRate'];
  }
}

class imageObject {
  final String public_id;
  final String url;

  imageObject({
    required this.public_id,
    required this.url,
  });
}

它给出了例外：未经手的例外：键入'list＆lt; dynamic＆gt;' ”的子类型

不是

product.image![0].url,

类型

的“列表

Answer 1

您还需要对 imageObject JSON数据进行估算。为此，您需要将 factory imageObject.fromjson（）构造函数添加到 imageObject 类中，就像您为ProductModel类所做的那样。

这是您需要的代码：

  class ProductModel {
  String? name;
  String? price;
  String? discountPrice;
  String? discountRate;
  String? category;
  String? description;
  List<imageObject>? image;

  ProductModel({
    required this.name,
    required this.price,
    this.category,
    this.description,
    this.discountPrice,
    this.discountRate,
    this.image,
  });

  factory ProductModel.fromJson(Map<String, dynamic> jsonData) => ProductModel(
        name: jsonData['name'] as String?,
        price: jsonData['price'] as String?,
        category: jsonData['category'] as String?,
        description: jsonData['Description'] as String?,
        discountPrice: jsonData['discountPrice'] as String?,
        discountRate: jsonData['discountRate'] as String?,
        
        //Have a good look here to understand how nested list of maps are deserialized

        image: (jsonData['imageUrls'] as List<dynamic>?)
            ?.map((e) => imageObject.fromJson(e as Map<String, dynamic>))
            .toList(),
      );
}

class imageObject {
  final String public_id;
  final String url;

  imageObject({
    required this.public_id,
    required this.url,
  });

  factory imageObject.fromJson(Map<String, dynamic> jsonData) => imageObject(
        public_id: jsonData['public_id'] as String,
        url: jsonData['url'] as String,
      );
}

我们在这里所做的是，将来自ImageUrls键的数据作为列表，并通过ImageObject方法的JSON构造函数映射每个单独的元素。

Answer 2

您必须将重新列表映射到ImageObject s列表。

1. 为您的imageObject类创建图形构造函数

class imageObject {
  final String public_id;
  final String url;

  imageObject({
    required this.public_id,
    required this.url,
  });
  imageObject.fromMap(Map<String, dynamic> map) => imageObject(public_id = map['public_id'], url = map['url'] );
}

2. 使用以下内容：

 ProductModel.fromMap(Map<String, dynamic> data) {
    
    name = data['name'];
    image = data['imageUrls'].map((map) => imageObject.fromMap(map) ); 
    category = data['category'];
    description = data['Description'];
    price = data['price'];
    discountPrice = data['discountPrice'];
    discountRate = data['discountRate'];
  }

您可能需要添加一些铸件或对先前的代码进行一些修改使其正常工作，但这是一般的想法。