ember: promise for a controller action that calls a service method - ember.js

Question

I have an action on my controller that calls a service method. The service method is an ember-data query. I need to return a message contained in that ember-data payload back to the controller (print it to the screen).
I am having a hard time figuring out how to get the controller action (function) to "wait" for the service method to finish.
The controller action:
// controller action
processCoupon() {
// the service method I want to wait for the response for
let messageObject = DS.PromiseObject.create({
promise: this.get('cart').processCoupon()
});
// the message
messageObject.then(response => {
let promo_message = messageObject.get('promo_message');
if (promo_message.message && promo_message.alert) {
if (!promo_message.success) {
// show error message in alert with ember-cli-notifcations
} else {
// show success message in alert with ember-cli-notifcations
}
}
});
},
Method in the service I want to wait for the response for:
// service method syncs cart info (containing promo) with the backend
// promo_message is in the response payload
processCoupon() {
return this.get('store').findRecord('cart', get(this, 'cartObj.id')).then(cart => {
cart.save().then(newCart => {
set(this, 'cartObj', newCart); // sets response to property on service
return newCart.get('promo_message');
});
});
},
the 'response' in the promise is empty, and the MessageObject itself has no content. So I'm doing something wrong here (and it's likely misunderstanding promises).
I messed around with RSVP promises and didn't do well there either. What am I missing, OR is there a better way to do this?

Answer 1

Your service method should return a promise. Then you can use it like this: this.get('cart').process().then((response) => {/*your code working with service's response*/});
You also should be aware that if you use ember data, it will return a model instance, not an original response from your back-end.
And, in order to return promise, you need to wrap your service's method in new Promise((resolve, reject) => {/*asynchronous code here*/});

Answer 2

I've done something similar with Ember.RSVP.Promise() is that what you want?
// controller
myMessage = null,
actions:
cartCoupon() {
let msg = this.get('cart').processCoupon();
msg.then(myDataMessage => this.set('myMessage', myDataMessage);
}
//service
processCoupon() {
return new Ember.RSVP.Promise( resolve => {
let data = this.get('store').findRecord('cart', get(this, 'cartObj.id')).then(cart => {
cart.save().then(newCart => {
set(this, 'cartObj', newCart); // sets response to property on service
return newCart.get('promo_message');
});
});
resolve(data);
});
}