CODEWITHSUNDEEP
javascriptnode.jspromiseq
Francisco Canela
Francisco Canela

Reputation: 1124

Node.js Q promises then() chaining not waiting

I am trying to refactor the following code to avoid the callback hell, transforming it into:

createUser(user_data)
  .then(createClient(client_data))
  .then(createClientPartner(clientpartner_data))
  .then(function(data) {
    cb(null, _.pick(data,['id','username']));
  }, function(error) {
    cb(error);
  });

As you see, I created a method for each one of the steps:

function createUser(user_data) {
  console.log('createUser');
  var deferred = Q.defer()

  new db.models.User.create(user_data, function(err, user) {
    console.log('createUser done');
    if (!!err)
      deferred.reject(err);
    else {
      client_data['id'] = user.id;
      deferred.resolve(user);
    }
  });

  return deferred.promise;
}

The other methods have identical console.log calls to be able to follow the execution path.

I would expect it to be:

But instead, it is:

Why does are the functions triggered when the previous promise have not been resolved? I expect "then" to wait until previous promise have been resolved or rejected to continue. Am I missing something important about promises?

Upvotes: 4

Views: 1139

Answers (1)

Denys Séguret
Denys Séguret

Reputation: 382150

The problem is you don't pass functions, but the result of function calls.

Instead of

createUser(user_data)
  .then(createClient(client_data))

you should have

createUser(user_data)
.then(function(user){
    createClient(client_data) // no need for the user ? really ?
})

Upvotes: 5

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