using promises with getCollection - rally

Question

I'm trying to figure out how to apply the promises infrastructure in the case where I'm looping through a list of portfolio items to extract data for highcharts use and need to retrieve data from the related user stories. The goal is to create a way to not attempt to instantiate the chart object until all async callbacks are completed. Here's a code snippet illustrating what I'm trying to do - in this example, the getCollection() method's callback function is not being executed until all of the outer loop features have been retrieved.
_.each(records, function(feature) {
var rname = (feature.get('Release')) ? feature.get('Release')._refObjectName: "None";
//various other feature record extraction steps
feature.getCollection('UserStories').load({
fetch: ['FormattedID', 'Name', 'InProgressDate','AcceptedDate'],
callback: function(stories, operation, success){
Ext.Array.each(stories, function(story) {
var storyname = story.get('FormattedID') + ': ' + story.get('Name');
// other chart data extraction steps
}
});
}
});
});

Answer 1

I'd check out the guide in the docs on working with promises, especially the section on retrieving hierarchical data:
https://help.rallydev.com/apps/2.0/doc/#!/guide/promises-section-retrieving-hierarchical-data
The basic idea is to keep an array of all the promises representing the child collection store loads and then to use a Deft.Promise.all to wait for them all to finish before continuing.
So something like this, based on your code above:
var childStoryPromises = [];
_.each(records, function(feature) {
var rname = (feature.get('Release')) ? feature.get('Release')._refObjectName: "None";
// various other feature record extraction steps
var userStoriesStore = feature.getCollection('UserStories');
var promise = userStoriesStore.load({
fetch: ['FormattedID', 'Name', 'InProgressDate','AcceptedDate']
});
childStoryPromises.push(promise);
feature.userStoriesStore = userStoriesStore; //save reference for later
});
//wait for all stores to load
Deft.Promise.all(childStoryPromises).then({
success: function() {
_.each(records, function(feature) {
var userStories = feature.userStoriesStore.getRange();
//extract user story data here
});
},
scope: this
});