Cocoon add association, how to limit number of associations

Question

I am creating a system that stores cards using Ruby/Rails/HAML - In this case there is a Card class that has many Colours (this is also a class). When creating and editing a card I am using the Cocoon gem to allow me to dynamically add colour associations.

The problem I am having is that in the Card model, a card is limited to having a maximum of 5 colours. Yet the interface allows adding of unlimited colours resulting in an error.

Is there a way in Cocoon to limit the number of associations that can be added to a form, so that this limit is not exceeded?

This is the code for a form to add/edit a Card

 = simple_form_for @card, multipart: true do |c|
  = c.input :name, label: "Name of the card"
  = c.input :cost, label: "Cost of the card"
  #colours
   = c.simple_fields_for :colours do |colour|
    = render "colour_fields", f: colour
   .links
    = link_to_add_association 'add colour', c, :colours

And this is the colour_fields form

.nested-fields
 = f.input :value, as: :select, collection: Colour::VALUES, selected: f.object.value, include_blank: false
 = link_to_remove_association "remove colour", f

Thanks in advance.

Answer 1

I would use javascript for this. You can bind to an event that is triggered upon insert of a new item: on this event count how many items there are, and hide the link if needed.

Likewise, when loading the page do the same.

So in code that would look like:

 $(function() {
   function check_to_hide_or_show_add_link() {
     if ($('#colours .nested-fields:visible').length == 5) {
       $('#colours .links a').hide();
     } else {
       $('#colours .links a').show();
     }
   }

   $('#colours').on('cocoon:after-insert', function() {
     check_to_hide_or_show_add_link();
   });

   $('#colours').on('cocoon:after-remove', function() {
     check_to_hide_or_show_add_link();
   });

   check_to_hide_or_show_add_link();     
 });

Something like this should work. Note this code is not tested :)

Hope this helps.