[Rails] Rails 101 - Validation

[Stefan Arentz]

I'm trying to figure out what the standard pattern is for simple form 
management.

Consider the following table:

  table country:
   int id
   int code
   varchar name

Like:

  1 45 Denmark
  2 31 The Netherlands

I have a controller to add a new one:

  class CountriesController

    def add
      @country = Country.new
    end

    def add_post
      @country = Country.new(@params["country"])
      if @country.save then
        redirect_to(:action => "list")
      else
        render_action "add"
      end
    end

  end

With a simple form: (the show error is a test of a helper that shows an 
optional error)

  <form action="add_post" method="post">
    Code: <%= text_field("country", "code") %> <%= show_error(@country, 
"code") %><br>
    Name: <%= text_field("country", "name") %><br>
    <input type="submit" value="Add country">
  </form>

Ok all looks simple. But my problem is with validation. My Country 
model object looks like this:

  class Country < ActiveRecord::Base
    def validate
      errors.add("code", "invalid") unless code =~ /[0-9]*/;
    end
  end

There are two problems with this code:

When I call /countries/add, the code form field is initialized to 0. I 
don't want to have a default value in there. Where does it come from?

Also, when I submit the form with the code form field set to '123a', 
the validation correctly kicks in and sets the error message. But it 
also resets the code field to '0'. The name field is displayed 
correctly however.

I'm not sure what I'm doing wrong here.

  S.