Tag Archives: ruby

Extending acts_as_commentable

acts_as_commentable is a nice little ruby on rails plugin. It extends your ActiveRecord classes giving them comments. We are going to use comments on all kinds of things, starting with recipes, of course. However, AAC lacks a critical feature: the ability for users to approve comments before they are displayed. In this post I am going to run through extending AAC using acts_as_state_machine.

The first thing I did (and do to all the plugins we use) was pistonize the plugin so I could hack on it without fear of getting my changes destroyed.

I start off simply here by adding two states to the Comment model: :pending and :approved.

class Comment < ActiveRecord::Base
  # The first element of this array is the initial state
  VALID_STATES = [ :pending, :approved ]
  acts_as_state_machine :initial => VALID_STATES[0]
 
  event :approve do
    transitions :from => :pending, :to => :approved
  end
 
  VALID_STATES.each do |_state|
    # Define _state as a state
    state _state
  end
 
  # More code snipped
end

Now we are going to write some real code, so here comes a little RSpec. aac provides three class methods:

class Comment < ActiveRecord::Base
  class << self
  # Helper class method to lookup all comments assigned
  # to all commentable types for a given user.
  def find_comments_by_user(user)
 
  # Helper class method to look up all comments for
  # commentable class name and commentable id.
  def find_comments_for_commentable(commentable_str, commentable_id)
 
  # Helper class method to look up a commentable object
  # given the commentable class name and id
  def find_commentable(commentable_str, commentable_id)
  end

Since it didn’t come with Test::Unit or RSpec tests I wrote up some test for these methods.

describe Comment, "class methods" do
  fixtures :comments, :recipes, :users
  it "should find comments by user" do
    Comment.find_comments_by_user( comments(:comment_one).user ).should all_belong_to( comments(:comment_one).user )
  end
 
  # This could be more specific
  it "should find comments for a particular class" do
    Comment.find_comments_for_commentable( Comments(:comment_one).commentable_type, comments(:comment_one).commentable_id ).should be_an_instance_of(Array)
  end
 
  it "should find all comments for a particular class" do
    # I happen to know that comment_one is a recipe comment
    Comment.find_commentable( "Recipe", comments(:comment_one).commentable_id ).should be_an_instance_of(Recipe)
  end
 
end

If you are confused by should all_belong_to then you should check out my previous post. With these specs out of the way we can go on to adding more new code.

  it "should find approved comments by user" do
    Comment.find_approved_comments_by_user( comments(:comment_one).user ).should all_be_in_state("approved")
  end
 
  it "should find pending comments by user" do
    Comment.find_pending_comments_by_user( comments(:comment_one).user ).should all_be_in_state("pending")
  end
end

Now, normally you would write one spec at a time, but I think I would bore my readers, so I combined these two. Also take note that I am using another custom RSpec matcher all_be_in_state(). It looks a lot like all_belong_to(), so I leave its implementation as an exercise to the reader (unless I can get another blog post out of it). To get these tests to pass I add a few lines of code:

  VALID_STATES.each do |_state|
    # Define _state as a state
    state _state
 
    # Add Comment.find__comments methods
    ( class &lt;&lt; self; self; end ).instance_eval do
      define_method "find_#{_state}_comments_by_user" do |_user|
        find_in_state( :all, _state, :conditions => ["user_id = ?", _user.id], :order => "created_at DESC" )
      end
    end
  end

I am not a method_missing kind of guy, and prefer the dynamic-method metaprogramming style. This lot of code defines class methods at runtime that find Comments in specific states. I am actually using whytheluckystiff’s metaid to hide some of the meta-junk, but I thought I should spell it out here for clarity.

Well, now we have a Comment class with two states and code to limit finds to cmments in a specific state. Right now, that is all I have. Here is the full code for the Comment class and the RSpec. You will see another custom RSpec matcher here, require_a().

class Comment < ActiveRecord::Base
 
  # The first element of this array is the initial state
  VALID_STATES = [ :pending, :approved ]
 
  acts_as_state_machine :initial => VALID_STATES[0]
 
  belongs_to :commentable, :polymorphic => true
  belongs_to :user
 
  event :approve do
    transitions :from => :pending, :to => :approved
  end
 
  validates_associated :user
  validates_presence_of :comment, :commentable_id, :commentable_type, :state,                           :user_id
 
  VALID_STATES.each do |_state|
    # Define _state as a state
    state _state
 
    # Add Comment.find_<state>_comments methods
    meta_def "find_#{_state}_comments_by_user" do |_user|
      find_in_state( :all, _state, :conditions => ["user_id = ?", _user.id],
                     :order => "created_at DESC" )
    end
  end
 
  class < < self
 
    # Helper class method to look up a commentable object
    # given the commentable class name and id
    def find_commentable(commentable_str, commentable_id)
      commentable_str.constantize.find(commentable_id)
    end
 
    # This could be refactored into find_<state>_comments_by_user (somehow)
    def find_comments_by_user(_user)
      find( :all, :conditions => ["user_id = ?", _user.id],
            :order => "created_at DESC" )
    end
 
    # Helper class method to look up all comments for
    # commentable class name and commentable id.
    def find_comments_for_commentable(commentable_str, commentable_id)
      find( :all,
            :conditions => [ "commentable_type = ? and commentable_id = ?",
                             commentable_str, commentable_id ],
            :order => "created_at DESC" )
    end
 
  end
 
end</state>
require File.dirname(__FILE__) + '/../../../../spec/spec_helper'
 
module CommentSpecHelper
 
end
 
describe Comment do
 
  fixtures :comments
 
  include CommentSpecHelper
 
  before(:each) do
    @comment = Comment.new
  end
 
  it "should start out in pending state" do
    @comment.state.should == "pending"
  end
 
  it "sould transition to approved" do
    @comment = comments(:pending_comment)
    @comment.approve!
    @comment.state.should == "approved"
  end
 
  it "should require a comment" do
    @comment.should require_a(:comment)
  end
 
  it "should require a commentable_id" do
    @comment.should require_a(:commentable_id)
  end
 
  it "should require a commentable_type" do
    @comment.should require_a(:commentable_type)
  end
 
  it "should require a state" do
    @comment.should require_a(:state)
  end
 
  it "should require a user_id" do
    @comment.should require_a(:user_id)
  end
 
end
 
describe Comment, "class methods" do
 
  fixtures :comments, :recipes, :users
 
  it "should find all comments for a particular class" do
    # I happen to know that comment_one is a recipe comment
    Comment.find_commentable( "Recipe", comments(:comment_one).commentable_id ).should be_an_instance_of(Recipe)
  end
 
  it "should find comments by user" do
    Comment.find_comments_by_user( comments(:comment_one).user ).should all_belong_to( comments(:comment_one).user )
  end
 
  it "should find approved comments by user" do
    Comment.find_approved_comments_by_user( comments(:comment_one).user ).should all_be_in_state("approved")
  end
 
  it "should find pending comments by user" do
    Comment.find_pending_comments_by_user( comments(:comment_one).user ).should all_be_in_state("pending")
  end
 
  # This could be more specific
  it "should find comments for a particular class" do
    Comment.find_comments_for_commentable( comments(:comment_one).commentable_type, comments(:comment_one).commentable_id ).should be_an_instance_of(Array)
  end
 
end

–Dean

belong_to RSpec matcher

I was extending acts_as_commentable and needed a good RSpec test to check the returned objects from its finder methods belonged to the correct user. For example, Comment.find_comments_by_user( :some_user ) should all belong_to :some_user. I’ll be darned if that doesn’t look like a RSpec description. Since there is no all_belong_to matcher, I wrote one.

module ActiveRecordValidations
  class BelongTo
    def initialize(expected)
      @expected = expected
    end
 
    def matches?(args)
      args.all? do |target|
        @target = target
        @target.send(@expected.class.to_s.downcase) == @expected
      end
    end
 
    def failure_message
      "expected #{@target.inspect} to all belong to #{@expected}"
    end
 
    def negative_failure_message
      "expected #{@target.inspect} not to all belong to #{@expected}"
    end
  end
 
  def belong_to(expected)
    BelongTo.new( [expected] )
  end
 
  def all_belong_to(expected)
    BelongTo.new( expected )
  end
end

The matches? method takes an array of objects and goes through them with all? checking that they have a belongs_to the expected thing. Using the example above, each comment object returned by Comment.find_comments_by_user would get tested if comment.user== @user.

–Dean

Concise Signup & Signin Pages

Login, Signup

We are presented with these quick forms all the time. While it is easy to create standard login and signup pages, Amazon.com has a good one:

Amazon Sigin Image

What makes it good?

First of all, the prompts are written in plain English. Amazon sells to a wide slice of the population, meaning that about 15% of their customers are probably not very technology-saavy. (-2?) Anything they can do to ease the operation helps their customers buy.

Secondly, when a user visits Amazon.com, there is only one link: “Your account” instead of separate login and signup links. Simple is generally better.

Also note the standard “forgot your password” link plus an additional “has your email address changed?” question. Both are useful to have close at hand.

Implementation

Rails 2.0 strongly encourages you to design RESTful applications. Login forms are associated with Session objects, while signup forms go with User objects (rather, Brewer objects in our case). A simple redirect in the SessionsController#create method takes care of pointing a user in the right direction.

class SessionsController &lt; ApplicationController
  def create
    if params[:signin_action] == 'new_user'
      redirect_to new_brewer_path( :brewer =&gt; {:email =&gt; params[:email]} )
    else
      # Do sigin stuff
    end
  end
end

Note that we pass params[:email] to the new_brewer_path so that field is automatically populated on the next page. If you are using the generated scaffold, you will have to change your BrewersController#new method to instantiate a new @brewer object:

class BrewersController &lt; ApplicationController
  def new
    @brewer = Brewer.new(params[:brewer])
  end
end

Lastly, here is the extra test:

class SessionsControllerTest &lt; Test::Unit::TestCase
  def test_should_redirect_to_new_brewer_if_asked
    an_email = "dean@brewsession.com"
    post :create, :email =&gt; an_email, :signin_action =&gt; 'new_user'
    assert_redirected_to new_brewer_path(:brewer =&gt; {:email =&gt; an_email} )
    assert_nil session[:brewer_id]
  end
end

In a later post I will talk about how to implement the change password action in a RESTful way.

–Dean

Hey, my first rails plugin

Ruby on Rails allows for plugins to extend its functionality. My first attempt at one is nothing special but I am going to blog about it anyway 😀

I needed a way to check if a number is within a range before saving a record to the database. Rails has a number of good validations built in, but not one that does that. In two or three hours, I was able to piece together a simple plugin that adds “validates_range_of” to my AR models. The code is a little ugly until I can get Greg to install a syntax highlighting plugin for this blog.

module ActiveRecord
module Validations
module ClassMethods
def validates_range_of(*attrs)
options = {  :on => :save  }
options.update(attrs.pop) if attrs.last.is_a?(Hash)
attrs.flatten!
unless options[:message]
if options[:maximum] && options[:minimum]
options[:message] = 'must be betweeen ' + options[:minimum].to_s + ' and ' + options[:maximum].to_s
elsif options[:maximum]
options[:message] = 'must be less than or equal to ' + options[:maximum].to_s
elsif options[:minimum]
options[:message] = 'must be greater than or equal to ' + options[:minimum].to_s
else
raise ArgumentError, 'Range unspecified.  Specify the :maximum and/or :minimum.'
end
end
 
validates_numericality_of( attrs, options )
 
validates_each(attrs, options) do |record, attr_name, value|
if ((!options[:maximum].nil?) && (!options[:minimum].nil?)) &&
(value > options[:maximum] || value < options[:minimum])
record.errors.add( attr_name, options[:message] )
elsif (!options[:maximum].nil?) && value > options[:maximum]
record.errors.add( attr_name, options[:message] )
elsif (!options[:minimum].nil?) && value < options[:minimum]
record.errors.add( attr_name, options[:message] )
end
end
end
end
end
end

As you can see this plugin extends AR::Validations. So my models can use validates_range_of to check minimum and maximum values. Let’s look at the BJCP Scoresheet I needed it for:

class BjcpScoresheet < ActiveRecord::Base
belongs_to :brew_session
validates_associated :brew_session
validates_range_of :brew_session_id, { :minimum => 1, :message => 'does not belong to a brew session' }
validates_range_of :aroma_score, { :minimum => 1, :maximum => 12, :only_integer => true }
validates_range_of :appearance_score, { :minimum => 1, :maximum => 3, :only_integer => true }
validates_range_of :flavor_score, { :minimum => 1, :maximum => 20, :only_integer => true }
validates_range_of :mouthfeel_score, { :minimum => 1, :maximum => 10, :only_integer => true }
validates_range_of :impression_score, { :minimum => 1, :maximum => 10, :only_integer => true }

How nice – reusable user input validation.

–Dean

Of all the things I miss….

Before the death of my drives I had a flexible Measurement class written up. As most of you know brewing involves all kinds of measurement – hop weights, boil volume, bitterness, etc. The class served as a base that more specific classes would inherit and provided the framework for converting between different measurement systems. For example, the SpecificGravity class would inherit Measurement and provide the conversion code to switch between SG and Plato.

The database would save the scalar and units and instantiate an aggregation of these two pieces. When the units changed, back into the database it went with the new values. It was very easy to work with, but took me quite a bit of time to write.

“Why not use one of the libraries already available?” you might ask. The short answer is that they do not fit my needs. Firstly, none of them produced objects that I could stuff in the database as a aggregation – most are intended as great extensions to various number classes. Secondly, and most importantly, none of them dealt with Bitterness, Color or Specific Gravity, which is really why I need a measurement class. Lastly, most of them only handled linear transformations:

m2 = a * m1 + b

To convert from SG to Plato you need to use a cubic polynomial, ugh.

So I wrote my own, then re-wrote it, and it was beautiful. Now I am re-engineering the whole thing. In addition, I’ll have to figure out where I got the Plato to SG reverse conversion. I remember trying to solve the cubic equation, then finding something that actually worked.

It is a little faster-going because I wrote it all before, but I had some tr1cky 31337 code in there that I will have to figure out again.

Always make sure your backups are working and current.

–Dean