Flutter如何将嵌套JSON映射为数据模型并访问属性，合并日期生成DateTime？

1. 手动创建Flutter数据模型 #

我们先创建单条书籍数据的Book类，再创建外层包含书籍列表的响应模型，同时通过getter实现年月字段合并为DateTime对象的逻辑：

class Book {
  final int bookId;
  final String bookName;
  final int yearPublished;
  final int monthPublished;
  final int weekPublished;

  // 直接合并年月生成DateTime对象，无日期字段时默认日为1即可
  DateTime get publishDateTime => DateTime(yearPublished, monthPublished, 1);

  Book({
    required this.bookId,
    required this.bookName,
    required this.yearPublished,
    required this.monthPublished,
    required this.weekPublished,
  });

  // JSON转模型方法
  factory Book.fromJson(Map<String, dynamic> json) {
    return Book(
      bookId: json['book_id'] as int,
      bookName: json['book_name'] as String,
      yearPublished: json['year_published'] as int,
      monthPublished: json['month_published'] as int,
      weekPublished: json['week_published'] as int,
    );
  }

  // 可选：模型转JSON方法
  Map<String, dynamic> toJson() {
    return {
      'book_id': bookId,
      'book_name': bookName,
      'year_published': yearPublished,
      'month_published': monthPublished,
      'week_published': weekPublished,
    };
  }
}

// 外层包含books数组的响应模型
class BooksResponse {
  final List<Book> books;

  BooksResponse({required this.books});

  factory BooksResponse.fromJson(Map<String, dynamic> json) {
    var booksList = json['books'] as List;
    List<Book> parsedBooks = booksList.map((item) => Book.fromJson(item)).toList();
    return BooksResponse(books: parsedBooks);
  }
}

如果你不想手写映射逻辑避免出错，可以使用官方json_serializable包自动生成fromJson/toJson代码，使用逻辑和上述手动实现的完全一致。

2. 模型调用与属性访问 #

// 假设你拿到的原始JSON数据存在rawJson变量中
Map<String, dynamic> rawJson = {
  "books": [
    {
      "book_id": 1,
      "book_name": "Harry Potter and the philosopher's stone",
      "year_published": 1997,
      "month_published": 6,
      "week_published": 25,
    },
    {
      "book_id": 2,
      "book_name": "Harry Potter and the chamber of secrets",
      "year_published": 1998,
      "month_published": 7,
      "week_published": 26,
    },
  ]
};

// 映射为模型对象
BooksResponse response = BooksResponse.fromJson(rawJson);

// 属性访问示例
// 读取第一本书的名称
String firstBookName = response.books[0].bookName;
// 读取第一本书合并后的发布日期
DateTime firstPublishTime = response.books[0].publishDateTime;
// 读取第二本书的发布年份
int secondBookYear = response.books[1].yearPublished;

内容的提问来源于stack exchange，提问作者FDjawid