sequelize.js - "has many through" Sequelize 中的关联

Question

假设我们有三个模型:

书籍

章节

段落

以下是他们的关联:

图书有很多章节 .

章节有很多段落 .

图书有很多段落 , 通过 章节 .

是否可以与 Sequelize 定义“有很多，通过”关系？如果是这样，如何？

以下是 Book、Chapter 和 Paragraph 的非常基本的模型:

// Book model
const Book = sequelize.define('Book', {
  id: {
    type: DataTypes.INTEGER,
    allowNull: false,
    primaryKey: true
  },
  title: {
    type: DataTypes.STRING
  }
}, {
  classMethods: {
    associate: (models) => {
      Book.hasMany(models.Chapter, {
        foreignKey: 'bookId',
        as: 'chapters'
      });
    }
    // How can you add an association for a book having many paragraphs, through chapters?
  }
});


// Chapter model
const Chapter = sequelize.define('Chapter', {
  id: {
    type: DataTypes.INTEGER,
    allowNull: false,
    primaryKey: true
  },
  title: {
    type: DataTypes.STRING
  }
}, {
  classMethods: {
    associate: (models) => {
      Chapter.hasMany(models.Paragraph, {
        foreignKey: 'chapterId',
        as: 'paragraphs'
      });

      Chapter.belongsTo(models.Book, {
        foreignKey: 'bookId'
      });
    }
  }
});


// Paragraph Model
const Paragraph = sequelize.define('Paragraph', {
  id: {
    type: DataTypes.INTEGER,
    allowNull: false,
    primaryKey: true
  },
  content: {
    type: DataTypes.TEXT
  }
}, {
  classMethods: {
    associate: (models) => {
      Paragraph.belongsTo(models.Chapter, {
        foreignKey: 'chapterId'
      });
    }
    // How can you add an association for paragraphs belonging to a book "through" chapters?
  }
});

Answer 1

不幸的是，没有这种可能性。你可以做的是创建一些 instanceMethods在两个 Book和 Paragraph模型喜欢 getParagraphs和 getBook为了检索关联元素

// in Book model
instanceMethods: {
    getParagraphs: function(options){
        options.include = [
            {
                model: sequelize.models.Chapter,
                attributes: [],
                where: {
                    bookId: this.get('id')
                }
            }
        ];

        return sequelize.models.Paragraph.findAll(options);
    }
}

上述方法将返回其章节属于指定书籍的所有段落。你可以对 getBook 做相反的事情在 Paragraph模型。

另一方面，为了检索包含所有章节及其段落的书籍，您只需执行 findAll嵌套 include (开玩笑地提醒一下)。