Include a Coffeescript file with ERB in a view

Question

This is giving me a major headache...

So I have an app which requires a sidebar that lists various information to do with a user's player. One section of this sidebar is a friends list. Now, when Player A sends a friend request to Player B, the request should be automatically logged in B's sidebar, and I intend to use WebSockets to do this.

Here is my cp.js.coffe.erb file (there's only a few snippets of ERB at the moment; there will be loads more and I rather get this working first):

$ ->
  $("#cp").accordion()

  if `"WebSocket" in window`
    socket = new WebSocket("ws://localhost:8080") 

  socket.onopen = =>
    console.log("Connection Open")
    init = {
      sender: "cp"
      action: "init"
      user:   <%= @user.id %>
      token:  <%= cookies["remember_token"] %>
    }

    socket.send(init.to_json)

  socket.onerror = (e)=>
    console.log(e)

  socket.onclose = =>
    console.log("Closed")

  socket.onmessage = (m)=>
    console.log("Recieved: #{m.data}")
    msg = m.data.JSON.parse
    switch msg.action
      when "ret_init"

      when "friend_udt"
        refreshFriend()

refreshFriend() ->
  html = "<%= j render 'layouts/friends' %>"
  $('#friends').empty()
  $('#friends').add(html)

Theoretically, the code itself works fine, the problem being that Rails doesn't let you use ERB in the assets pipeline, and so this file has to sit in app/views/layouts . the file cannot access the variables declared within a controller or use the render method (or most other ERB methods).

Here's the thing: I can't include said file in my application.html.erb file, and I looked into requesting the file with AJAX, but from my understanding that will immediately execute the Javascript once and once only, and I need the methods in this to be constantly available to update the sidebar.

Is there any way of including this file so that it works with the ERB and the CoffeScript so that it would be continuously avaliable to the page? Am I misunderstanding the whole AJAX requesting method?

---

Thanks @nzifnab for your help with the JS. Now my friends partial looks like this:

 <ul id="friendlist"> <% if Relation.find_by(owner: @user.id, type: "freq") != nil %> <% Relation.find_by(owner: @user.id, type: "freq").each do |r| %> <li class="friend-request-cp"><%= link_to "/#{User.find(r.character).name}" %></li> <% end %> <% end %> <% if Relation.find_by(owner: @user.id, type: "friend") != nil %> <% Relation.find_by(owner: @user.id, type: "friend").each do |r| %> <li class="friend-cp"><%= link_to "/#{User.find(r.character).name}" %></li> <% end %> <% end %> </ul> 

I need to apply two different styles to each item, hence why I'm using the ERB here. This works fine, as it's loaded when the page is first navigated to, but my code was supposed to re-render that partial every time a notification comes through of any new interactions. It would then repopulate the list using the data from the database again. Is there a more efficient way of doing this? Can I still do this with the hamlcoffeeassets gem you showed me?

---

Slight tangent ensues:
By the way, I'm using Ruby 2.0.0-p247 and Rails 4 on Windows 7 . I felt the need to include that because of some major compatibility issues with gems that are much different from Ubuntu. I had to move from Ubuntu to Windows because updating from 13.04 to 13.10 broke everything Ruby Gem on that OS. I don't have tome to find a fix: I literally have only four days to get this app built.

Answer 1

You can kinda use erb in the asset pipeline, but you have to remember that it only gets rendered ONCE, EVER, and not once for every user and so even if there was an @user variable (which there won't be), it would never change. You can use erb in your coffee file for things like route paths and environment variables, but not for things like user-specific config and dynamic changes to the JS. It's bad practice anyway.

What you should really do is use a javascript library to read cookies instead of trying to do it with rails (This will give you access to some of the things you appear to be trying to do). And when you need more dynamic behavior you should render data-attributes or other values into the html DOM itself and use the javascript to read that.

Take a look at this cookie library: https://github.com/carhartl/jquery-cookie

There's many others to look at via a quick google search.

socket.onopen = =>
  console.log("Connection Open")
  init = {
    sender: "cp"
    action: "init"
    user:  $.cookie('user_id')
    token:  $.cookie('remember_token')
  }

There are a couple of ways to render new markup for your view using JS. One way is to use js templates. I'm a big fan of the hamlcoffeeassets library here: https://github.com/netzpirat/haml_coffee_assets Although it uses haml for the view, and not ERB. There are ERB variants as well.

You would add some markup to app/assets/templates/friend.jst.hamlc like so:

%p This is my friend markup #{@friend.name}

And then you can render it from your JS like this:

$('#friends').append(JST['templates/friend'](friend: {name: 'Bob'}))

Which will append the markup from your template with the values you've passed interpolated in. In my example you'd end up with this markup inside your #friends container:

<p>This is my friend markup Bob</p>

Alternatively you can render the partial you want via rails into your JSON response as just a string, and then insert that into your document...

So your JS might look something like this:

socket.onmessage = (m)=>
  console.log("Recieved: #{m.data}")
  msg = m.data.JSON.parse
  switch msg.action
    when "ret_init"

    when "friend_udt"
      refreshFriend(msg.friendHTML)

refreshFriend(html) ->
  $('#friends').html(html)

UPDATE

In reference to your ERB question... First of all your partial is incredibly inefficient making similar calls to the database four times every time you render it. haml_coffee_assets is for use with the haml markup language (which I prefer over ERB), if you want ERB then use eco instead: https://github.com/sstephenson/eco

If you want to render this in the JS, then you need to send this "friend relation" data as JSON through the notification data response, you do not have access to active record OR any controller methods or instance variables when rendering javascript partials - they don't hit back to the server, they only use what is accessible by your javascript at the time.

Answer 2

This should really go to app/assets/javascripts/cp.js.coffee.erb , you can use erb in the asset pipeline just fine (see here ) Make sure you are spelling the coffee extension right, though!

Doing this, you should be able to call this via ajax without problems, the path would be /assets/cp.js .

Answer 3

try this gem: ' coffeebeans '

1. name your coffee file as "some_file.html.erb"

    <%= coffeescript_tag_do %> # your coffee script here ... <% end %> 

2. in another erb file:

    <%= render file: '.../some_file' %>