Conditional Rails Form Validation

Question

I have a rails model that has two field attributes: :commission_fixed & :commission_percentage. The user should only be able to choose between one of the two options either: :commission_fixed or :commission_percentage not both on form submit. Is this possible using Rails validation? If so what is the best way to achieve this?

Keep a dropdown or select option , what's stopping you . You can use jquery to stop multiple selection on radio buttons . — Caffeine Coder
– Caffeine Coder, Commented Oct 30, 2014 at 6:14
@CaffeineCoder How can we make select box for two attributes, is it possible AFAIK We can send options to a single attribute as select box right — anusha
– anusha, Commented Oct 30, 2014 at 6:15
Thanks for the response. I know I can achieve it this way, my questions was more out of curiosity and if it can be achieved purely through using Rails validation. — Thomas Taylor
– Thomas Taylor, Commented Oct 30, 2014 at 6:17
If you just want to validate a particular field , then you can do so by mentioning presence: true in the attribute model — Caffeine Coder
– Caffeine Coder, Commented Oct 30, 2014 at 6:26
Thanks @CaffeineCoder I comfortable with Rails validation just wanting to know if my above question is possible. — Thomas Taylor
– Thomas Taylor, Commented Oct 30, 2014 at 6:30

Andrew Sinner · Accepted Answer · 2014-10-30 08:16:46Z

1

Your problem is within the way you've structured your column names / model attributes.

Ideally you should change your attribute names on your model to :commission_method and :commission_rate. This allows for greater flexibility. Then in your view you can achieve what you're looking for with a radio button. You can store your :commission_rate as a decimal in the db.

<%= f.radio_button :commission_method, "Fixed" %>
<%= f.radio_button :commission_method, "Percentage" %>
<%= f.number_field :commission_rate %>

In your view files if you need to switch between showing a fixed amount and a percentage you can just do:

<% case @sales_associate.commission_method %>
<% when 'Fixed' %>
  <span>Fixed: <%= number_to_currency(@sales_associate.commission_rate) %></span>
<% when 'Percentage' %>
  <span>Percentage: <%= "% #{@sales_associate.commission_rate}" %></span>
<% end %>

However, you "could" write a custom validation method that throws an error if both attributes were assigned.

In whatever model:

class SalesAssociate
   validate :only_one_selected_commission

   def only_one_selected_commission
     errors[:base] << "Please select only one form of commission" if self.commission_fixed.present? && self.commission_percentage.present?
   end
end

answered Oct 30, 2014 at 8:16

Andrew Sinner

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1 Comment

Thomas Taylor Over a year ago

Thank you for such a wonderful, well informed and articulate answer. I see what you mean with the column names / model attributes I will rewrite this to reflect your answer. Cheers

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