同步执行Sequelize查询

Question

我正在使用Node.js和Sequelize(使用Postgres后端)构建一个网站.我有一个返回许多带有外键的对象的查询,我想传递给外键引用的对象列表.

在示例中,Attendances包含Hackathon密钥,我想返回一个黑客马拉松列表.由于代码是异步的,因此以下内容在Node中不起作用:

models.Attendance.findAll({
    where: {
        UserId: req.user.id
    }
}).then(function (data) {
    var hacks = [];
    for (var d in data) {
        models.Hackathon.findOne({
            where: {
                id: data[d].id
            }
        }).then(function (data1) {
            hacks.append(data1);
        });
    }
    res.render('dashboard/index.ejs', {title: 'My Hackathons', user: req.user, hacks: hacks});
});

有没有办法以同步方式进行查询,这意味着我不会返回视图,直到我有"hacks"列表填充所有对象？

谢谢!

Answer 1

使用Promise.all来执行所有的查询,然后调用一个函数.

models.Attendance.findAll({
    where: {
        UserId: req.user.id
    }
}).then(function (data) {
    // get an array of the data keys, (not sure if you need to do this)
    // it is unclear whether data is an object of users or an array. I assume
    // it's an object as you used a `for in` loop
    const keys = Object.keys(data)
    // map the data keys to [Promise(query), Promise(query), {...}]
    const hacks = keys.map((d) => {
      return models.Hackathon.findOne({
        where: {
          id: data[d].id
        }
      })
    })
    // user Promise.all to resolve all of the promises asynchronously
    Promise.all(hacks)
      // this will be called once all promises have resolved so
      // you can modify your data. it will be an array of the returned values
      .then((users) => {
        const [user1, user2, {...}] = users
        res.render('dashboard/index.ejs', {
          title: 'My Hackathons', 
          user: req.user, 
          hacks: users
        });
      })
});