Meteor.call x Meteor.callAsync

TIP

It is recommened to use Meteor.callAsync instead of Meteor.call because of how our async API works. Meteor.call is still available but it is not recommended to use it, it can lead to unexpected behavior.

Using Meteor.callAsync will make your code more predictable and easier to maintain.

Example of how to migrate from Meteor.call to Meteor.callAsync:

v2-client.jsx

import { Meteor } from 'meteor/meteor'

let data, error;

Meteor.call('getAllData', (err, res) => { 
  if (err) {
    error = err;
  } else {
    data = res;
  }
});

// render data or error

v2-server.js

import { Meteor } from 'meteor/meteor'
import { Mongo } from 'meteor/mongo'

const MyCollection = new Mongo.Collection('myCollection');

Meteor.methods({
  getAllData() {
    return MyCollection.find().fetch(); 
  }
});

v3-client.jsx

import { Meteor } from 'meteor/meteor'

try {
  const data = await Meteor.callAsync('getAllData'); 
  // render data
} catch (error) {
  // render error
}

v3-server.js

import { Meteor } from 'meteor/meteor'
import { Mongo } from 'meteor/mongo'

const MyCollection = new Mongo.Collection('myCollection');

Meteor.methods({
  async getAllData() {
    return await MyCollection.find().fetchAsync(); 
  }
});

Rules of using Meteor.callAsync & Meteor.call

TIP

It is not recommended to use concurrent calls. Use await for your Meteor.callAsync.

here are a few examples of cases where you should use Meteor.callAsync instead of Meteor.call:

import { Meteor } from 'meteor/meteor'

Meteor.call("someMethod", (err, res) => { This is not ok
  if (err) {
    console.log(err);
  } else {
    console.log(res);
  }
});


Meteor.callAsync('someMethod') This is not ok
  .then(data => console.log(data))
  .catch(err => console.log(err));

// it is not recommended to use concurrent calls

Promise.all([  This is not ok
  Meteor.callAsync('someMethod'),
  Meteor.callAsync('someMethod')
]).then(([data1, data2]) => {
  console.log(data1, data2);
});

// Ok section

Meteor.call("someMethod", (err, res) => { 
  if (err) {
    console.log(err);
  } else {
    console.log(res);
  }
});

await Meteor.callAsync('someMethod') // this is ok

// this is also ok
Meteor.callAsync('someMethod').then(data => { 
  console.log(data);
  Meteor.callAsync('someMethod').then(data2 => {
    console.log(data2);
  });
});