如何从 Firestore 子集合中获取数据？

Question

下面是产品集合的 Firebase Firestore 数据库，代码能够从集合中获取所有其他数据，但只有颜色字段返回 null，我正在使用 strembuilder 以及产品和颜色模型。

如果您知道我如何实现这一点，我将竭诚为您提供帮助。

产品型号

class Product with ChangeNotifier {
  String id;
  String title;
  String description;
  String price;
  String category;
  String currency;
  String condition;
  String firestoreid;
  String images;
  Seller seller;
  ProductColor colors;
  Offer offer;
  double rating;
  bool isFavourite;
  bool approved;

  Product({
    this.id,
    this.title,
    this.description,
    this.category,
    this.images,
    this.colors,
    this.rating,
    this.price,
    this.seller,
    this.currency,
    this.condition,
    this.firestoreid,
    this.approved,
    this.isFavourite,
    this.offer,
  });

  Product copy(
    String id,
    String title,
    String description,
    String price,
    String category,
    String currency,
    String condition,
    String firestoreid,
    String images,
    Seller seller,
    ProductColor colors,
    Offer offer,
    double rating,
    bool isFavourite,
    bool approved,
  ) =>
      Product(
        id: id ?? this.id,
        title: title ?? this.title,
        description: description ?? this.description,
        price: price ?? this.price,
        category: category ?? this.category,
        currency: currency ?? this.currency,
        condition: condition ?? this.condition,
        firestoreid: firestoreid ?? this.firestoreid,
        images: images ?? this.images,
        seller: seller ?? this.seller,
        colors: colors ?? this.colors,
        offer: offer ?? this.offer,
        rating: rating ?? this.rating,
        isFavourite: isFavourite ?? this.isFavourite,
        approved: approved ?? this.approved,
      );

  static Product fromJson(Map<String, dynamic> json) => Product(
        id: json['firestore_id'],
        title: json['productName'],
        description: json['productDescriptions'],
        category: json['categoryName'],
        images: json['image'],
        colors: ProductColor.fromJson(json['color']),
        rating: json[''],
        price: json['price'],
        seller: Seller.froJson(json['seller']),
        approved: json['approved'],
        currency: json['priceCurrency'],
        condition: json['productCondition'],
        firestoreid: json['firestore_id'],
      );
}

颜色模型

class ProductColor {
  String id;
  Color color;
  String qty;
  String size;

  ProductColor({
    this.id,
    this.color,
    this.qty,
    this.size,
  });

  static ProductColor fromJson(Map<String, dynamic> json) => ProductColor(
        id: json[''],
        color: json['color'],
        qty: json['qty'],
        size: json['size'],
      );

  Map<String, dynamic> toJson() => {
        'id': id,
        'color': color,
        'qty': qty,
        'size': size,
      };
}

Answer 1

这里的问题是字段color 被保存为Array 内的Array。这意味着您使用的这段代码：

  static ProductColor fromJson(Map<String, dynamic> json) => ProductColor(
        id: json[''],
        color: json['color'],
        qty: json['qty'],
        size: json['size'],
      );

不会工作，因为它需要 Object。

您可以更改保存数据的方式，使其保存为Object，或者更改fromJson，使其能够正确读取嵌套Array 的数据。