Trouble to synchronise promises in Node.js using Q - node.js

Question

I am currently doing an API in Node.JS with the framework Sails.js. I am using promises for the first time and I have some troubles to sync my promises like I want.
My main function is the following :
createCard: function(req, res) {
checkIfUserHasStripeAccount(req.user)
.then(addCreditCardToStripeAccount())
.then(function cardCreated() {
res.send(200, {
msg: 'Card created'
});
})
.catch(function handleError(err) {
res.send(err.httpCode, err.msg);
})
},
Obviously I can't add a credit card to a stripe account if the user doesn't have one.
The function checkIfUserHasStripeAccount() checks if the account exists and if not, create it.
Here is the code for this part :
function checkIfUserHasStripeAccount(user) {
var deferred = q.defer();
if (!user.idStripe) {
createStripeAccountToUser(user)
.then(function(savedUser) {
deferred.resolve(savedUser);
})
.catch(function(err) {
deferred.reject(err);
})
} else {
deferred.resolve(user);
}
return deferred.promise;
}
function createStripeAccountToUser(user) {
var deferred = q.defer();
var jsonUserToCreate = {
description: user.firstname + ' ' + user.surname,
email: user.email
};
stripe.customers.create(jsonUserToCreate, function(err, customer) {
if (err) {
deferred.reject({
httpCode: 500,
msg: 'some error'
});
} else {
user.idStripe = customer.id;
user.save(function(err, savedUser) {
if (err) {
deferred.reject({
httpCode: 500,
msg: 'some error'
});
}
deferred.resolve(savedUser);
});
}
});
return deferred.promise;
}
The problem is that the .then(addCreditCardToStripeAccount()) is executed before checkIfUserHasStripeAccount() is finished.
I can't figure out why. I thought the .then(addCreditCardToStripeAccount()) would only be executed if it received a reject or resolve.

Answer 1

You are correct in your line of thought.
The problem is that you are invoking your function instead of referencing it:
.then(addCreditCardToStripeAccount())
should be:
.then(addCreditCardToStripeAccount)
I expect this to work:
createCard: function (req, res) {
checkIfUserHasStripeAccount(req.user)
.then(addCreditCardToStripeAccount)
.then(function cardCreated(){
res.send(200, {msg: 'Card created'});
})
.catch(function handleError(err) {
res.send(err.httpCode, err.msg);
})
},
For future, note that the () after the function name invokes the function, as order of execution in JS will evaluate it first due to being inside the then's ().
In promise chains, always invoke only the first function. Example:
function first () { /*...*/ } // All return promise.
function second() { /*...*/ }
function third () { /*...*/ }
first() // Invoked
.then(second) // Not invoked. second() will have been bad here.
.then(third);