Rails - Make ajax request from javascript event and load partial - ruby-on-rails

Question

what's up?
I'm using rails 3.2.3 with ruby 1.9.2p290.
I have a model Purchase which has many purchase_payments:
class Purchase < ActiveRecord::Base
has_many :purchase_payments, :class_name => 'PurchasePayment', :dependent => :destroy
accepts_nested_attributes_for :purchase_payments
def Purchase.build_payments(count)
#Creat #count payments with some logic for each of them
end
end
In my form, I have number_field:
<td>
<%= f.number_field :payments_count, :min => 0 %>
</td>
Now, I'd like to have the purchase_payment fields appear based on the number of payments. For that, I have a specific div:
<div id="purchase_payments_space"> </div>
Every resource I've found so far, talks about ajax generated by helper tags, like link_to ... , :remote => true, but using this tags, the user would have to click on the link to have the remote function called. In other part of my app, I use jquery ajax request and I'm trying to use like this for sending the request to my controller:
function load_payments() {
$.ajax({
type: "POST",
url: "/purchases/build_payments/" + document.getElementById("purchase_payments_count").value,
});
}
$(document).ready(function() {
$("#purchase_payments_count").change(load_payments);
}
In my controller, I have the respond_to :js right after my class declaration and the following method:
def build_payments
pc = params[:payments_count].to_i
#purchase = Purchase.new
#purchase_payments = Purchase.build_payments pc
respond_to do |format|
format.js
end
end
This way I have my app/views/purchases/buid_payments.js.erb run ok.
The thing is, I'm building a collection of payments that should be included in my form, and doing things the way I'm currently doing doesn't look like rails would do this. This way I will have to write much code in the js.erb file and still I can't figure out how I'll make the create method build the complete purchase from the params (I don't know how to build the form from the javascript).
I looked at several different ways but none have given an integrated solution for making an ajax request from a javascript event and have the view create the nested fields for my nested attributes (its a collection of purchase_payment I must remember).
I saw http://railscasts.com/episodes/196-nested-model-form-part-1 and http://railscasts.com/episodes/197-nested-model-form-part-2 but those build on top of helper methods like link_to and link_to_function.
Can anyone point me how can I accomplish that?

Answer 1

$.ajax({
url: "purchases/build_payments",
type: 'POST',
data: $('#purchase_payments_count').val(),
dataType: 'html',
headers: {
'X-CSRF-Token': '<%= form_authenticity_token.to_s %>'
}
});
then
def build_payments
pc = params[:payments_count].to_i
#purchase = Purchase.new
#purchase_payments = Purchase.build_payments pc
respond_to do |f|
f.js {}
end
end
which will run buid_payments.js.erb which can populate\recreate your table
If can't see it I can't help you.