与 Sequelize 的嵌套关系答案

【问题标题】：Nested relations with Sequelize与 Sequelize 的嵌套关系
【发布时间】：2014-08-08 14:20:57
【问题描述】：

我正在使用带有 Node + MySQL 的 Sequelize。

我有一个类似这样的模型结构：

// models:
var Group, Issue, Invite;

// many Issues per Group
Group.hasMany(Issue);
Issue.belongsTo(Group);

// Groups can invite other Groups to work on their Issues
Issue.hasMany(Invite, {foreignKey: groupId});
Invite.belongsTo(Issue, {foreignKey: groupId});
Group.hasMany(Invite, {foreignKey: inviteeId});
Invite.belongsTo(Group, {foreignKey: inviteeId});

// given an Issue id, include all Invites + invited Groups (inviteeId) - But how?
var query = {
    where: {id: ...}, 
    include: ???
};
Issue.find(query).complete(function(err, issue) {
    var invites = issue.invites;
    var firstInvitedGroup = issue.invites[0].group;
    // ...
});

这有可能吗？有哪些可能的解决方法？谢谢！

【问题讨论】：

标签： javascript mysql sequelize.js

【解决方案1】：

Sequelize Docs: Nested Eager Loading

示例

Issue.find({
    include: [
        {
            model: Invite,
            include: [Group]
        }
    ]
});

【讨论】：

【解决方案2】：

如果您想预先加载所有嵌套关联，请使用此功能。

Issue.find({
    include:getNestedAssociations(Issue)
});



//Recursively load all bested associtiaons
function getNestedAssociations(_model) {
  const associations = [];
  for (const association of Object.keys(_model.associations)) {
    const model = _model.associations[association].target;
    const as = association;
    const include = getNestedAssociations(model);
    associations.push({
      model: model,
      as: as,
      ...(include && { include: include }),
    });
  }
  return associations;
}

【讨论】：

【解决方案3】：

在失去所有希望之后，我终于尝试了一个有效的随机命中。只发送带有空数组的属性，然后它不会包含在结果中

{
    model: User,
    as: 'users',
    attributes: [],  // This will work//
    where: {
      user_id: 1
    }
  }

【讨论】：