Cocoon add association, how to limit number of associations

问题

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.

回答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.

回答2:

I had a similar task to do and what I ended up doing was putting an onclick event on the "Add" link. This onclick event will execute before the code to add the fields is executed.

In your case, the code would look something like the following:

= link_to_add_association 'add colour', c, :colours, class: 'add-colour-link'

Then in your JavaScript (CoffeeScript in this case):

$('.add-colour-link').on 'click', (e) ->
   if $('#colours .nested-fields:visible').size() < 5
     return true #continue the execution 
   else
     #maybe display the modal to the user that only a maximum of 5 is allowed
     return false #prevent further execution

来源：https://stackoverflow.com/questions/12934925/cocoon-add-association-how-to-limit-number-of-associations