So far, we have implemented an MVC application under Ruby in Rails, and provided a rudimentary form to allow the user to add rows to the model. In this section, we show you the extra code needed to validate the data, and to echo it back out to the user within the form if it's incorrect.

1. In the model, add some calls to provide criteria against which to validate

  class Product < ActiveRecord::Base
    validates_presence_of :pname, :unitprice, :stocklevel
    validates_numericality_of :unitprice, :stocklevel
    validates_uniqueness_of :pname
  end

2. In the controller, add code to see if the save of the new record worked

  def saveproduct
    @newprod = Product.new(params[:product])
    if @newprod.save # And checks the object
      redirect_to :action => "index" # to method (above)
    else
      @main_result = "Please correct"
      render :action => "addproduct" # using view
    end
  end

3. Add the error messages to the view:

  <% form_for(@newprod, :url => "/productlister/saveproduct") do |fieldname| %>
    <%= fieldname.error_messages %>
  
    <%= fieldname.label :pname %>
    Name of product <%= fieldname.text_field :pname %><br />
  
    <%= fieldname.label :unitprice %>
    Price Each <%= fieldname.text_field :unitprice %><br />
  
    <%= fieldname.label :stocklevel %>
    Initial Stock Held <%= fieldname.text_field :stocklevel %><br />
  
    <%= fieldname.submit "Done!" %><br />
  <% end %><br />

This is one of a series of summaries taking you from initial installation of Ruby and Rails through to a complete multitable application: [link] - Installing Ruby and Rails [link] - Hello World, Ruby on Rails Style [link] - What and Why - Model, View, Controller [link] - Multiple views, same model [link] - A form to allow data to be added to the model [link] - Validating data entries for storage in the model [link] - Cleanly viewing model data [link] - Complete sample, including a multiple table model These topics are covered on our Introduction to Rails day - an optional extension of Ruby Programming or Learning to program in Ruby

(written 2012-06-23)

 R202 - Ruby on Rails
  [1050] The HTML++ Metalanguage - (2007-01-22)
  [1302] Ruby, Ruby, Ruby. Rails, Rails, Rails. - (2007-08-13)
  [1375] Python v Ruby - (2007-10-02)
  [1745] Moodle, Drupal, Django (and Rails) - (2008-08-08)
  [2605] Ruby on Rails - a sample application to teach you how - (2010-01-30)
  [2607] Answers on Ruby on Rails - (2010-01-30)
  [2609] Scope of variables - important to Ruby on Rails - (2010-01-31)
  [3624] Why do we need a Model, View, Controller architecture? - (2012-02-25)
  [3756] Ruby on Rails - how it flows, and where the files go - (2012-06-08)
  [3772] Hello World - Ruby on Rails - a checklist of each step - (2012-06-22)
  [3777] Multiple views in a single appication - sharing common parts of the template - Ruby on Rails - (2012-06-23)
  [3778] Providing a form to allow the user to add data to the model - Ruby on Rails - (2012-06-23)
  [3780] Ruby of Rails - cleanly displaying model data in the view - (2012-06-23)
  [3919] What is a web framework? - (2012-11-10)
  [4010] Really Simple Rails - (2013-02-17)
  [4013] Web Frameworks - nested templates - (2013-02-22)

Back to Providing a form to allow the user to add data to the model - Ruby on Rails

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Forward to Ruby of Rails - cleanly displaying model data in the view

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