CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-3
Tintin81
Tintin81

Reputation: 10207

How to calculate a default value for a form text field in Ruby on Rails?

I have a form for payments like this:

<%= f.label :invoice_id %>
<%= f.select(:invoice_id, current_user.outstanding_invoices_collection) %>

<%= f.label :amount %>
<%= f.text_field :amount %>

I wonder if there's a way to populate the value of the amount text field somehow, e.g. with the open balance of the associated invoice?

In my Invoice model have this function:

def balance
  payments.map(&:amount).sum - total
end

How can this be done?

Upvotes: 2

Views: 1240

Answers (2)

Samiron
Samiron

Reputation: 5317

Im assuming you want to populate the text box based on the selection of a invoice from dropdown. In that case

The idea is

  • You need to make a ajax call onchange of the invoice dropdown.
  • That ajax response should update the value of the text box.

And with rails-3 i think its recommended to do this in unrobustive way. Here is a link you can follow. Start playing with it meanwhile I will try to make something functional. Hope to get a good result again.

Are you looking for how to populate the value only?

Update:

Here is the ajax part

#Application.js or any sutable js file
$(function($) {
    $("#your_drop_down_id").change(function() {
        #Your the url to your controller action here
        $.ajax({url: '/get_amount',
        data: 'invoice_id=' + this.value,
        dataType: 'script'})
    });
});

#in get_amount Action
invoice = Invoice.find(params[:invoice_id]) #Other appropriate logic to get the invoice
@amount = invoice.balance

#get_amount.js.erb
$('#your_text_box_id').val('<%= @amount %>');

#routes.rb
#This part is written following the gist: https://gist.github.com/3889180 by @TinTin
resources :payments do  
   collection do
       get 'get_amount'
   end
end

Let me know if any part is confusing to you.

Upvotes: 2

Matzi
Matzi

Reputation: 13925

In your controller you can assign any value to any field, and it will be displayed in the view.

def new
  @payment = new Payment()
  @payment.amount = 100
end

If you want some dynamic value, e.g: based on a combobox selection, then do it in javascript or with AJAX.

Upvotes: 1

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