Rails 3: creating a validation with :if statement

Hi I'm trying to setup a validation that is only called in a specific form view, to do this I'm trying to create a hidden_field for a virtual 开发者_如何学编程attribute on the form and set this to a value, then validate :if the virtual attribute equals the value.

So far I have:

## user model 

validates_presence_of :password_confirmation, :if => :confirmation_validation 

attr_accessible :email, :password, :password_confirmation, 
 :remember_me, :name, :avatar, :username, :bio, :confirmation_validation

def confirmation_validation
 # not sure what goes here???
end


## form view


<%= form_for(resource, :validate => true, :as => resource_name, :url => registration_path(resource_name), :html => { :method => :put }, :html => {:multipart => true}) do |f| %>
<%= devise_error_messages! %>

<p><%= f.label :password %> <i>(leave blank if you don't want to change it)</i><br />
<%= f.password_field :password %></p>

<p><%= f.label :password_confirmation %><br />
<%= f.password_field :password_confirmation %>
<% f.hidden_field :confirmation_validation, :value => 100%></p>

<p><%= f.submit "Update" %></p>
<% end %>

---

The value of the confirmation_validation hidden field should be included in the params hash, and also set the virtual attribute accordingly. Therefore, you can probably simply check whether or not the value has been set:

validates_presence_of :password_confirmation, :if => :should_confirm?

def should_confirm?
  confirmation_validation == '100' # Value of the hidden field as set in the form
end

---

write one line code, it could help you to organize your code in simple.

validates_presence_of :password_confirmation, :if => lambda {|u| confirmation_validation == '100'}

or

validates_presence_of :password_confirmation, :if => Proc.new {|u| confirmation_validation == '100'}

---

This response is very late, but for future SO viewers, I think the answer to @Rajesh question

Hey, the above is showing an error for me and the error is given below. Cant mass-assign protected attributes. Why?

Is that you need to remove the hidden field you are using as a flag from the params hash before it's assigned to the record. Something like

params.reject{|p| p == name_of_hidden_field}