sequelize ORM asynchronous method calls - node.js

Question

How can I call methods asynchronously in sequelize ORM? (because I have to use returned value inside other methods).
user.dao.js:
var User = require('./user.model');
class UserDao {
constructor() {}
insert(user) {
var pk;
User.sync({ force: false }).then(() => {
User.create(user).then(function(user) {
console.log('Entry successful from dao: ' +
JSON.stringify(user));
//return generated pk
pk = user.id;
console.log('ID: ' + pk);
});
});
return pk;
}
user.test.js:
class UserDaoTest {
constructor() {
this.userDao = new UserDao();
this.compare = new UtilsObject();
}
/*
all CRUD method calls
*/
testAll() {
this.testInsert();
this.testUpdate();
//this.testDelete();
//this.testRead();
//this.compare();
}
/*
insert method
*/
testInsert() {
// composite form
var user = {
name: 'nisha',
email: 'nisha#gmail.com',
phoneNo: 8978,
picUrl: 'nisha',
description: 'SI',
status: 'active',
waitingTime: 10,
rating: 7
};
/*
calling insert user with above data
*/
var pk = this.userDao.insert(user);
console.log('pk value: ' + pk);
//var obj1 = this.userDao.readById(pk);
console.log('obj1 value: ' + user);
//this.testReadById(obj1);
}
testReadById(obj1) {
var obj2 = this.userDao.readById(obj1);
this.compare.compare(obj1, obj2);
this.testDelete(obj1);
}
}
export default UserDaoTest;
Here in user.test.js, in testInsert() method want to get the value of pk which is returned from insert() method of user.dao.js, but right now I am getting pk value as undefined.

Answer 1

Use a promise chain.
Suppose you need to get an entry for a particular user & do some operations on it.
Model.User.findById(someId)
.then((user) => {
// Do something with user.
})
You shouldn't be calling methods synchronously, NodeJs is not designed this way. It works with callbacks or promises.

Answer 2

Your code won't work because it is async code.
Watch the famous Youtube video about the event loop
But in short, if you will run the following example, which is like your code but without your logic:
var User = require('./user.model');
class UserDao {
constructor() {}
insert(user) {
var pk;
console.log('1');
User.sync({ force: false }).then(() => {
pk = 123;
console.log('3');
});
console.log('2');
return pk;
}
The variable pk will be undefined and your console will look like this:
1
2
3
If you want it to work, you should "wait" for the async functions like this:
var User = require('./user.model');
class UserDao {
constructor() {}
// #return Promise
insert(user) {
return User.sync({ force: false }).then(() => {
return User.create(user)
}).then((user) => {
console.log('Entry successful from dao: ' + JSON.stringify(user));
return user.id
})
}
And when you use it:
class UserDaoTest {
constructor() {
this.userDao = new UserDao();
this.compare = new UtilsObject();
}
/*
all CRUD method calls
*/
testAll() {
// if testInsert and testUpdate can run simultaneously you can keep it like this.
// Otherwise, use Promise.then as well
this.testInsert();
this.testUpdate();
}
/*
insert method
*/
testInsert() {
var user = {
// ...
};
/*
calling insert user with above data
*/
this.userDao.insert(user).then((userId) => {
// YOUR COMPARE CODE
}).then(done); // Where done is a function to let you test framework that you async code is done
}
}
export default UserDaoTest;
Another way of doing that is using the new async and await. That way you will get a code which is more readable and maintainable.
You can read more here