Using Design Documents to add an element to a list - couchdb

Question

Users can press a button on my website to declare interest in a course. For every course there is a document in my CouchDB installation. These documents look like this:
{
"_id": "...",
"_rev": "...",
"name": "...",
"description": "...",
"userList": []
}
When a users presses the button his name should be added to "userList". I wrote a Design Document for this:
{
"_id": "_design/updateList",
"_rev": "...",
"updates": {
"addUser": "function(doc, req) {doc['userList'] = req['name']; var message = 'user added'; return [doc, message];}",
}
}
I know that this cannot be the right solution because the list can never be longer than one user name like this. However, not even that works. When I press on the button, the line ""userList": []" disappears from the corresponding document.
What's the problem here? I use PHP-On-Couch to run the Design Document but there shouldn't be any problems in my PHP code. I see in the CouchDB log that CouchDB receives the user name just fine.

Answer 1

The direct problem is that a req object does not have a field called "name" so:
doc['userList'] = req['name']
is equivalent to:
doc['userList'] = undefined
you may have meant to use userCtx req.userCtx.name directly if users are logged in, or req.query.name if you have added it as a parameter.
More generally, you probably meant to push their name on to the array which is probably fine if class sign up isn't very high volume. An alternate approach is to generate an independent document for each user+class and rely on views to count them.