Properly embed JavaScript variables in Ruby on Rails 4.x

Question

I am using Ruby on Rails 4 and am trying to write a JavaScript that requires server-side data to populate. For instance, I might have a control called StudentsController and I want to return all particular students from a particular class. So in my controller I might do:

def index
  @students = Student.all
end

I then have a script in /app/assets/javascripts/ called foo.js and in there I'm trying to split the students up by their class_id.

in foo.js

$(function() {
    var class_a = <%= @students.select { |s| s.class_id = 'a' }.to_json %>
    var class_b = <%= @students.select { |s| s.class_id = 'b' }.to_json %>
})

Problem is class_a is null when I'm checking on the browser side of things. I'm assuming foo.js isn't linked up to StudentsController and doesn't see @students. What's the right way to wire JavaScript this way so I can have access to javascript variables with my server-side objects?

Try to use the gon gem

apneadiving
– apneadiving

2014-02-24 21:05:32 +00:00
Commented Feb 24, 2014 at 21:05 — apneadiving
– apneadiving, Commented Feb 24, 2014 at 21:05

benjaminjosephw · Accepted Answer · 2014-02-24 21:14:42Z

2

One problem here is simply that your file should be called foo.js.erb to compile ruby.

Also, I think you want to do this:

var class_a = <%= @students.select { |s| s.class_id == 'a' }.to_json %>

(Notice the double equal sign)

You might even be better to find the specific student in your controller and pass each through individually - this would be a better separation of concerns and would keep this logic out of your views.

edited Feb 24, 2014 at 21:14

answered Feb 24, 2014 at 21:09

benjaminjosephw

4,4273 gold badges23 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

randombits Over a year ago

Do I then have to add foo.js to my HTML?

benjaminjosephw Over a year ago

You should checkout the docs on the Asset Pipeline to understand how it all works together: guides.rubyonrails.org/asset_pipeline.html

Collectives™ on Stack Overflow

Properly embed JavaScript variables in Ruby on Rails 4.x

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related