Promises in Sequelize: how to get results from each promise

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时光取名叫无心
时光取名叫无心 2021-02-19 19:45

In Sequelize >=1.7 we can use promises

Can you explain for me how can i get values from each user in this code:

var User = sequelize.define(\"user\", {
          


        
3条回答
  •  清歌不尽
    2021-02-19 20:39

    Using no additional libraries (and if you need to maintain the order of creates), you can do this by simply creating variable(s) in the enclosing scope which hold the values:

    var created = {};
    User
      .sync({ force: true })
      .then(function() { return User.create({ username: 'John' }) })
      .then(function(john) { created.john = john; return User.create({ username: 'Jane' }) })
      .then(function(jane) { created.jane = jane; return User.create({ username: 'Pete' }) })
      .then(function(pete) {
        created.pete = pete;
    
        console.log("we just created 3 users :)")
        console.log("this is pete:")
        console.log(created.pete.values)
    
        // what i want:
        console.log("this is jane:")
        console.log(created.jane.values)
    
        console.log("this is john:")
        console.log(created.john.values)
      })
    

    In general though, I would recommend that you lean towards @Bergi's answer which creates a list of Promises and waits for all of the promises to complete.

    Edit based on question update:

    Using your updated code block and building on @Bergi's suggestion of Promise.map, you can avoid using variables in a higher scope with something like the following:

    User.hasMany(Group)
    Group.hasMany(User)
    
    User
      .sync({ force: true })
      .then(function() {
        var users = Promise.map( ['John', 'Jane', 'Pete'], function(name) {
          return User.create({ username: name });
        });
        var group = Group.findOrCreate({id: 1});
        return Promise.all([group, users]);
      })
      .spread(function(group, users) {return group.setUsers(users)})
      .then(function(result) { console.log(result)})
    })
    

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