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You’re currently reading the article “Active Record Associations and Validations with Resouce Mapping in Ruby on Rails.”

Published:: February 19th 09:19 AM

Updated:: August 17th 07:48 PM

Sections:: Ruby on Rails

Active Record Associations and Validations with Resouce Mapping in Ruby on Rails

The following article describes how model validation and association within Rails following resource mapping. I also briefly describe how to automatically annotate models and generate rails documentation.

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The following posts are based on a Ruby on Rails workshop I am teaching in Thimphu, Bhutan. It is not a complete tutorial since it does not include explanations. It may in the future but I do not know when I will have time to add them, so I am publishing it now as is to make it available to others that may find it useful. The sketches describe how to progressively build an Image Management System from the ground-up.

Before reading this article it is recommended that you read this first: RESTful Controllers.

Index

Generating Rails Docs
Annotating Models
Generating Administrative Levels and Administrative Units
Validating and Associating
Updating the Controllers and Views
- Countries' show
- AdministrativeLevels' Actions
  - new
  - index
  - show
  - edit
  - destroy
- The Whole AdministrativeLevels Controller

Generating Rails Docs

You make available the rails documentation by creating a new project, freezing rails, and rdocumenting all libraries (make sure you do this at the workspace folder and NOT at the IMS folder):

rails dummy_app
cd dummy_app
rake rails:freeze:gems
echo >vendor/rails/activesupport/README
rake doc:rails

Annotating Models

On the previous article, we created a table called countries. To make the attributes available from the Ruby code, we can install the rails task annotate_models by typing into the command-line:

ruby script/plugin install http://svn.pragprog.com/Public/plugins/annotate_models

You run it by typing into the command-line:

rake annotate_models

Now you will see the countries' field information as comments in app/models/country.rb:

# == Schema Information
# Schema version: 1
#
# Table name: countries
#
#  id    :integer(11)   not null, primary key
#  title :string(255)   
#

class Country < ActiveRecord::Base
end

Notice that an auto-number id was greated automatically.

Generating Administrative Levels and Administrative Units

Now we will have a table administrative_levels to store for each country the name of each level of its administrative divisions (for instance, the highest level division of Bhutan is a "District", for United States a "State", for China a "Province", for Guatemala a "Department", etc.). We create it similarly to before:

ruby script/generate scaffold_resource administrative_level country_id:integer level:integer title:string

Ensure that the table uses MyISAM and limit to the title by updating app/db/migrate/002_create_administrative_levels to:

class CreateAdministrativeLevels < ActiveRecord::Migration
  def self.up
    create_table :administrative_levels, :options => 'engine=MyISAM' do |t|
      t.column :country_id, :integer
      t.column :level, :integer
      t.column :title, :string, :limit => 100
    end
  end

  def self.down
    drop_table :administrative_levels
  end
end

We will also have a table administrative_units to store the actual unit names of the countries at each level:

ruby script/generate scaffold_resource administrative_unit administrative_level_id:integer parent_administrative_unit_id:integer title:string

Again ensure that the table uses MyISAM and limit to the title by updating app/db/migrate/003_create_administrative_units to:

class CreateAdministrativeUnits < ActiveRecord::Migration
  def self.up
    create_table :administrative_units, :options => 'engine=MyISAM' do |t|
      t.column :administrative_level_id, :integer
      t.column :parent_administrative_unit_id, :integer
      t.column :title, :string, :limit => 100
    end
  end

  def self.down
    drop_table :administrative_units
  end
end

Run migration:

rake db:migrate

And update models with attribute information:

rake annotate_models

Validating and Associating

Add validations and associations to app/models/country.rb:

# == Schema Information
# Schema version: 3
#
# Table name: countries
#
#  id    :integer(11)   not null, primary key
#  title :string(255)   
#

class Country < ActiveRecord::Base
  validates_presence_of :title
  validates_uniqueness_of :title
  has_many :administrativeLevels
end

app/models/administrative_level.rb:

# == Schema Information
# Schema version: 3
#
# Table name: administrative_levels
#
#  id         :integer(11)   not null, primary key
# country_id :integer(11)   
#  level      :integer(11)   
#  title      :string(100)   
#

class AdministrativeLevel < ActiveRecord::Base
  validates_presence_of :country_id, :level, :title
  validates_numericality_of :level, :only_integer => true
  belongs_to :country
  has_many :administrativeUnits
end

and app/models/administrative_unit.rb:

# == Schema Information
# Schema version: 3
#
# Table name: administrative_units
#
#  id                            :integer(11)   not null, primary key
#  administrative_level_id       :integer(11)   
# parent_administrative_unit_id :integer(11)   
#  title                         :string(100)   
#

class AdministrativeUnit < ActiveRecord::Base
  validates_presence_of :administrative_level_id, :title
  belongs_to :administrativeLevel
  belongs_to :parentUnit, :class_name => 'AdministrativeUnit', :foreign_key => 'parent_administrative_unit_id'
end

Updating the Controllers and Views

Countries' show

Since the administrative levels depend on the countries, we have to tie it with the countries' views. First we want to display the administrative levels when displaying a countries' information. This is done by the show action in countries controller. To pass administrative level information to the view, update it to:

  # GET /countries/1
  # GET /countries/1.xml
  def show
    @country = Country.find(params[:id])
    @administrative_levels = @country.administrativeLevels

    respond_to do |format|
      format.html # show.rhtml
      format.xml  { render :xml => @country.to_xml }
    end
  end

To display the administrative levels and display a link to create new administrative levels, add update app/views/countries/show.rhtml to:

<p>
  <b>Title:</b>
  <%=h @country.title %>
</p>
<p><b>Administrative Levels</b> (<%= link_to 'New administrative level', new_administrative_level_path(:country_id => @country) %>)</p>
<ul>
<% for level in @administrative_levels %>
     <li><%= link_to h(level.title), administrative_level_path(level) %> (<%= level.level %>)</li>
<% end %>
</ul>

<%= link_to 'Edit', edit_country_path(@country) %> |
<%= link_to 'Destroy', country_path(@country), :confirm => 'Are you sure?', :method => :delete %> |
<%= link_to 'Back', countries_path %>

Notice that the country_id is sent with the new_administration_level_path.

AdministrativeLevels' new

Update the new action in the administrative_levels controller to:

  # GET /administrative_levels/new?country_id=1
  def new
    begin
      @country = Country.find(params[:country_id])
    rescue ActiveRecord::RecordNotFound
      logger.error("Attempt to access invalid country #{params[:country_id]}")
      redirect_to countries_path
    else
      @administrative_level = AdministrativeLevel.new(:country => @country)
    end
  end

The view should be changed to display the country name to the end-user and pass the country_id in the form post (as a hidden field) for the attribute to be there when writing it to the database in the create action within the administrative_levels controller. Update app/views/administrative_levels/new.rhtml

<h1>New administrative level</h1>

<%= error_messages_for :administrative_level %>

<% form_for(:administrative_level, :url => administrative_levels_path) do |f| %>
     <p>
       <b>Country</b><br />
       <%= f.hidden_field :country_id %>
       <%= link_to h(@country.title), country_path(@country) %>
     </p>

     <p>
       <b>Level</b><br />
       <%= f.text_field :level %>
     </p>

     <p>
       <b>Title</b><br />
       <%= f.text_field :title %>
     </p>

     <p>
       <%= submit_tag "Create" %>
     </p>
<% end %>

<%= link_to 'Back', administrative_levels_path(:country_id => @country) %>

Notice that the back link is sending the country_id to administrative_levels_path, which will be rendered by the index action in the administrative_levels controller.

AdministrativeLevels' index

To receive the country_id and pass the country's administrative levels to the view, update the index action within the administrative_levels controller to:

  # GET /administrative_levels?country_id=1
  # GET /administrative_levels.xml?country_id=1
  def index
    begin
      @country = Country.find(params[:country_id])
    rescue ActiveRecord::RecordNotFound
      logger.error("Attempt to access invalid country #{params[:country_id]}")
      redirect_to countries_path
    else    
      @administrative_levels = @country.administrativeLevels

      respond_to do |format|
        format.html # index.rhtml
        format.xml  { render :xml => @administrative_levels.to_xml }
      end
    end
  end

Now update the app/views/administrative_levels/index.rhtml for it to be rendered properly:

<h1>Listing administrative levels in <%= link_to h(@country.title), country_path(@country) %></h1>

<table border="1">
   <tr>
     <th>Level</th>
     <th>Title</th>
   </tr>

<% for administrative_level in @administrative_levels %>
   <tr>
     <td><%=h administrative_level.level %></td>
     <td><%= link_to h(administrative_level.title), administrative_level_path(administrative_level) %></td>
   </tr>
<% end %>
</table>

<br />

<%= link_to 'New administrative level', new_administrative_level_path(:country_id => @country) %> |
<%= link_to 'Back', country_path(@country) %>

Notice that the country_id is sent, as before, to the new_administrative_level_path. We have added a back link to the index view that points to the country for which the administrative levels are displayed. The name of the administrative levels are made links (just as we did for the countries) to the show action. The show action does not need the country_id, since it is part of the administrative_level.

AdministrativeLevels' show

The show action in the administrative_levels controller gets the country from the administrative_level. Update it to:

  # GET /administrative_levels/1
  # GET /administrative_levels/1.xml
  def show
    @administrative_level = AdministrativeLevel.find(params[:id])
    @country = @administrative_level.country

    respond_to do |format|
      format.html # show.rhtml
      format.xml  { render :xml => @administrative_level.to_xml }
    end
  end

The view should display the name of the country instead of its id. Update app/views/administrative_levels/show.rhtml to:

<p>
  <b>Country:</b>
  <%=link_to h(@country.title), country_path(@country) %>
</p>

<p>
  <b>Level:</b>
  <%=h @administrative_level.level %>
</p>

<p>
  <b>Title:</b>
  <%=h @administrative_level.title %>
</p>


<%= link_to 'Edit', edit_administrative_level_path(@administrative_level) %> |
<%= link_to 'Destroy', administrative_level_path(@administrative_level), :confirm => 'Are you sure?', :method => :delete %> |
<%= link_to 'Back', administrative_levels_path(:country_id => @country) %>

As before the back link passes the country_id to the administrative_levels_path.

AdministrativeLevels' edit

The edit action in the administrative_levels controller should display the country names in a drop down list (instead of a text field for the country_id). To pass all countries to the view, update it to:

  # GET /administrative_levels/1;edit
  def edit
    @countries = Country.find(:all)
    @administrative_level = AdministrativeLevel.find(params[:id])
  end

Update app/views/administrative_levels/edit.rhtml to:

<h1>Editing administrative level</h1>

<%= error_messages_for :administrative_level %>

<% form_for(:administrative_level, :url => administrative_level_path(@administrative_level), :html => { :method => :put }) do |f| %>
   <p>
     <b>Country</b><br />
     <%= select('administrative_level', 'country_id', @countries.collect {|c| [ h(c.title), c.id ] }, { :include_blank => false }) %> (<%= link_to 'New country', new_country_path %>)
   </p>

   <p>
     <b>Level</b><br />
     <%= f.text_field :level %>
   </p>

   <p>
     <b>Title</b><br />
     <%= f.text_field :title %>
   </p>

   <p>
     <%= submit_tag "Update" %>
   </p>
<% end %>

<%= link_to 'Show', administrative_level_path(@administrative_level) %> |
<%= link_to 'Back', administrative_levels_path(:country_id => @administrative_level.country) %>

AdministrativeLevels' destroy

Finally, the destroy action in the administrative_levels controller should save the country before deleting the administrative level to redirect properly to the administrative_levels' index. Update it to:

  # DELETE /administrative_levels/1
  # DELETE /administrative_levels/1.xml
  def destroy
    @administrative_level = AdministrativeLevel.find(params[:id])
    country = @administrative_level.country
    @administrative_level.destroy

    respond_to do |format|
      format.html { redirect_to administrative_levels_url(:country_id => country) }
      format.xml  { head :ok }
    end
  end

The Whole AdministrativeLevels Controller

Taking into account all changes, the full administrative_levels controller should look like this:

class AdministrativeLevelsController < ApplicationController
  # GET /administrative_levels?country_id=1
  # GET /administrative_levels.xml?country_id=1
  def index
    begin
      @country = Country.find(params[:country_id])
    rescue ActiveRecord::RecordNotFound
      logger.error("Attempt to access invalid country #{params[:country_id]}")
      redirect_to countries_path
    else    
      @administrative_levels = @country.administrativeLevels

      respond_to do |format|
        format.html # index.rhtml
        format.xml  { render :xml => @administrative_levels.to_xml }
      end
    end
  end

  # GET /administrative_levels/1
  # GET /administrative_levels/1.xml
  def show
    @administrative_level = AdministrativeLevel.find(params[:id])
    @country = @administrative_level.country

    respond_to do |format|
      format.html # show.rhtml
      format.xml  { render :xml => @administrative_level.to_xml }
    end
  end

  # GET /administrative_levels/new?country_id=1
  def new
    begin
      @country = Country.find(params[:country_id])
    rescue ActiveRecord::RecordNotFound
      logger.error("Attempt to access invalid country #{params[:country_id]}")
      redirect_to countries_path
    else
      @administrative_level = AdministrativeLevel.new(:country => @country)
    end
  end

  # GET /administrative_levels/1;edit
  def edit
    @countries = Country.find(:all)
    @administrative_level = AdministrativeLevel.find(params[:id])
  end

  # POST /administrative_levels
  # POST /administrative_levels.xml
  def create
    @administrative_level = AdministrativeLevel.new(params[:administrative_level])

    respond_to do |format|
      if @administrative_level.save
        flash[:notice] = 'AdministrativeLevel was successfully created.'
        format.html { redirect_to administrative_level_url(@administrative_level) }
        format.xml  { head :created, :location => administrative_level_url(@administrative_level) }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @administrative_level.errors.to_xml }
      end
    end
  end

  # PUT /administrative_levels/1
  # PUT /administrative_levels/1.xml
  def update
    @administrative_level = AdministrativeLevel.find(params[:id])

    respond_to do |format|
      if @administrative_level.update_attributes(params[:administrative_level])
        flash[:notice] = 'AdministrativeLevel was successfully updated.'
        format.html { redirect_to administrative_level_url(@administrative_level) }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @administrative_level.errors.to_xml }
      end
    end
  end

  # DELETE /administrative_levels/1
  # DELETE /administrative_levels/1.xml
  def destroy
    @administrative_level = AdministrativeLevel.find(params[:id])
    country = @administrative_level.country
    @administrative_level.destroy

    respond_to do |format|
      format.html { redirect_to administrative_levels_url(:country_id => country) }
      format.xml  { head :ok }
    end
  end
end

Next recommended article to read: Introduction to Active Support

Technorati tags: ruby on rails, ruby-on-rails, Ruby, Rails

Liked it? !

Posted on February 19th | 4 comments | Filed Under: Ruby on Rails

4 comments

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saket 04.20.07 / 05AM
its good.
Tomasz Gorski 05.28.07 / 10AM
Thanks for very interesting article. btw. I really enjoyed reading all of your posts. Itâ€™s interesting to read ideas, and observations from someone elseâ€™s point of viewâ€¦ makes you think more. So please keep up the great work. Greetings
Manny 11.28.07 / 06AM
Hi, Thank you very much for this example, i was finding it hard to come by a tutorial of master detail style relationships using REST. If you allow me to make a correction, as i ran through it and the next article, references to childrenUnits were throwing exceptions because the administrative_units.rb model is missing a line: has_many :childrenUnits, :class_name => 'AdministrativeUnit', :foreign_key => "parent_administrative_unit_id" After adding that it all worked. Perhaps this happened to me because i'm using stable rails instead of Edge. Thanks again. -M
prezenty 05.28.08 / 17PM
This is interesting article, I did not it think that it yes. Interesting it knew persons about this how much. Sorry if I wrote bad there now my English is novice and I do not it write yet good.

About this entry

Active Record Associations and Validations with Resouce Mapping in Ruby on Rails

Liked it? !

Index

Generating Rails Docs

Annotating Models

Generating Administrative Levels and Administrative Units

Validating and Associating

Updating the Controllers and Views

Countries' show

AdministrativeLevels' new

AdministrativeLevels' index

AdministrativeLevels' show

AdministrativeLevels' edit

AdministrativeLevels' destroy

The Whole AdministrativeLevels Controller

Technorati tags: ruby on rails, ruby-on-rails, Ruby, Rails

Liked it? !

4 comments

Have your say

Articles in Ruby on Rails

	Thoughts and Experiences

About this entry

Active Record Associations and Validations with Resouce Mapping in Ruby on Rails

Liked it? digg_url = 'http://www.gaugeus.com/ramblings/2007/2/19/active-record-associations-and-validations-with-resouce-mapping-in-ruby-on-rails'; digg_skin = 'compact'; digg_bgcolor='#6C533A'; !

Index

Generating Rails Docs

Annotating Models

Generating Administrative Levels and Administrative Units

Validating and Associating

Updating the Controllers and Views

Countries' show

AdministrativeLevels' new

AdministrativeLevels' index

AdministrativeLevels' show

AdministrativeLevels' edit

AdministrativeLevels' destroy

The Whole AdministrativeLevels Controller

Technorati tags: ruby on rails, ruby-on-rails, Ruby, Rails

Liked it? digg_url = 'http://www.gaugeus.com/ramblings/2007/2/19/active-record-associations-and-validations-with-resouce-mapping-in-ruby-on-rails'; digg_skin = 'compact'; digg_bgcolor='#6C533A'; !

4 comments

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Articles in Ruby on Rails

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