Meteor, publish:composite. how to access joined data in the template? - meteor

Question

So I used publishComposite to do a collection join in Meteor. I have a parent collection (Subscriptions) with a user_id foreign key. I look up the user name in the Meteor.users collection to get the actual username, but how do I actually print this in the html template. My subscription data is there but how do I actually refer to the username?
Here is the publish code:
//publish subscriptions course view
Meteor.publishComposite('adminCourseSubscriptions', function(courseId){
return {
//get the subs for the selected course
find: function(){
return Subscriptions.find(
{course_id: courseId}
);
},
children:
[
{
//get the subscriber details for the course
find: function(sub){
return Meteor.users.find({_id:sub.user_id});
}
}
]
};
});
here are the template subdcriptions:
Template.adminCourseDetail.helpers({
courseDetail: function(id){
var id = FlowRouter.getParam('id');
return Courses.findOne({ _id: id });
},
courseSubscriptions: function(){
var id = FlowRouter.getParam('id');
return Subscriptions.find({course_id:id})
},
users: function(){
return Meteor.users.find();
}
});
and the template (which is garbage) ps the course details come from a separate collection. It was easier and I think more performant to get the details separately and this works fine. It's just the username that I cannot display correctly:
<template name="adminCourseDetail">
<h1>Course Details</h1>
<p>Title: {{courseDetail.title}}</p>
<p>Description: {{courseDetail.description}}</p>
<p>Start Date: {{courseDetail.startDate}}</p>
<p>Number of sessions: {{courseDetail.sessions}}</p>
<p>Duration: {{courseDetail.duration}}</p>
<p>Price: {{courseDetail.price}}</p>
<p>{{userTest}}</p>
edit
delete
<h2>Course Subscriptions</h2>
{{#each courseSubscriptions}}
<div class="row">
<div class="col-md-3">{{username}}</div>
<div class="col-md-3">{{sub_date}}</div>
</div>
{{/each}}
</template>
Thanks in advance for any suggestions!

Answer 1

As far as I understand your question, documents of the Subscriptions collection contain only the attribute user_id, referencing the corresponding user document in the Meteor.users collection. If this is the case, then you need to add an additional template helper which returns the username:
Template.adminCourseDetail.helpers({
// ...
getUsername: function() {
if (this.user_id) {
let user = Meteor.users.find({
_id: this.user_id
});
return user && user.username;
}
return "Anonymous";
}
// ...
});
After that, just replace {{username}} with {{getUsername}}:
<template name="adminCourseDetail">
<!-- ... -->
<h2>Course Subscriptions</h2>
{{#each courseSubscriptions}}
<div class="row">
<div class="col-md-3">{{getUsername}}</div>
<div class="col-md-3">{{sub_date}}</div>
</div>
{{/each}}
<!-- ... -->
</template>
Probably you misunderstood the concept of the reywood:publish-composite package. Using Meteor.publishComposite(...) will just publish a reactive join, but it will not return a new set of joined data.

Answer 2

For anyone else having a similar issue and looking at my specfic example. In my case the following code worked. Based on Matthias' answer:
In the template helper:
getUsername: function() {
let user = Meteor.users.findOne({
_id: this.user_id
});
return user;
}
and then in the template:
{{getUsername.username}}
My each block is looping through the cursor returned from the subscriptions collection rather than the course collection which is why it is simpler than the code Matthias provided.