Initial implementation.

Gemfile.lock

@@ -6,7 +6,15 @@ PATH
 GEM
   remote: http://gems.simplesideias.com.br/
   specs:
+    coderay (0.9.8)
     diff-lcs (1.1.3)
+    method_source (0.6.6)
+      ruby_parser (~> 2.0.5)
+    pry (0.9.6.2)
+      coderay (~> 0.9.8)
+      method_source (~> 0.6.5)
+      ruby_parser (~> 2.0.5)
+      slop (~> 2.1.0)
     rake (0.9.2)
     rspec (2.7.0)
       rspec-core (~> 2.7.0)
@@ -16,11 +24,16 @@ GEM
     rspec-expectations (2.7.0)
       diff-lcs (~> 1.1.2)
     rspec-mocks (2.7.0)
+    ruby_parser (2.0.6)
+      sexp_processor (~> 3.0)
+    sexp_processor (3.0.7)
+    slop (2.1.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
+  pry
   rake
   rspec (~> 2.7)
   simple_presenter!

README.rdoc

@@ -8,7 +8,45 @@ Some description
 
 == Usage
 
-Usage info
+  class User < ActiveRecord::Base
+    # implements the following attributes: name, email, password_hash, password_salt
+  end
+
+  class UserPresenter < Presenter
+    expose :name, :email
+  end
+
+  user = UserPresenter.new(User.first)
+  users = UserPresenter.map(User.all)
+
+If you're using Simple Presenter within Rails, presenters also have access to:
+
+* route helpers: just use the <tt>routes</tt> or <tt>r</tt> methods
+* view helpers: just use the <tt>helpers</tt> or <tt>h</tt> methods
+* I18n methods: just use the <tt>translate</tt>, <tt>t</tt>, <tt>localize</tt> or <tt>l</tt> methods
+
+For additional usage, check the specs.
+
+== TO-DO
+
+* Recognize ActiveRecord objects and automatically expose attributes used by url and form helpers (like <tt>Model.model_name</tt>, <tt>Model#to_key</tt>, and <tt>Model#to_param</tt>).
+* Override <tt>respond_to?</tt> to reflect exposed attributes.
+
+== Troubleshooting
+
+If you're having problems because already have a class/module called Presenter that is conflicting with this gem, you can require the namespace and inherit from <tt>SimplePresenter::Base</tt>.
+
+  require "simple_presenter/namespace"
+
+  class UserPresenter < SimplePresenter::Base
+  end
+
+If you're using Rails/Bundler or something like that, remember to override the <tt>:require</tt> option.
+
+  # Gemfile
+  source :rubygems
+
+  gem "simple_presenter", :require => "simple_presenter/namespace"
 
 == Maintainer
 

lib/simple_presenter/base.rb

@@ -1,4 +1,96 @@
 module SimplePresenter
   class Base
+    # Define how many subjects this presenter will receive.
+    # Each subject will create a private method with the same name.
+    #
+    # The first subject name will be used as default, thus isn't required as <tt>:with</tt>
+    # option on the SimplePresenter::Base.expose method.
+    #
+    #   class CommentPresenter < Presenter
+    #     subjects :comment, :post
+    #     expose :body                  # will expose comment.body
+    #     expose :title, :with => :post # will expose post.title
+    #   end
+    #
+    def self.subjects(*names)
+      @subjects ||= [:subject]
+      @subjects = names unless names.empty?
+      @subjects
+    end
+
+    # This method will return a presenter for each item of collection.
+    #
+    #   users = UserPresenter.map(User.all)
+    #
+    # If your presenter accepts more than one subject, you can provided
+    # them as following parameters.
+    #
+    #   comments = CommentPresenter.map(post.comment.all, post)
+    #
+    def self.map(collection, *subjects)
+      collection.map {|item| new(item, *subjects)}
+    end
+
+    # The list of attributes that will be exposed.
+    #
+    #   class UserPresenter < Presenter
+    #     expose :name, :email
+    #   end
+    #
+    # You can also expose an attribute from a composition.
+    #
+    #   class CommentPresenter < Presenter
+    #     expose :body, :created_at
+    #     expose :name, :with => :user
+    #   end
+    #
+    # The presenter above will expose the methods +body+, +created_at+, and +user_name+.
+    #
+    def self.expose(*attrs)
+      options = attrs.pop if attrs.last.kind_of?(Hash)
+      options ||= {}
+
+      attrs.each do |attr_name|
+        subject = options.fetch(:with, nil)
+        method_name = [subject, attr_name].compact.join("_")
+
+        class_eval <<-RUBY, __FILE__, __LINE__ + 1
+          def #{method_name}                                    # def user_name
+            proxy_message(#{subject.inspect}, "#{attr_name}")   #   proxy_message("user", "name")
+          end                                                   # end
+        RUBY
+      end
+    end
+
+    # It assigns the subjects.
+    #
+    #   user = UserPresenter.new(User.first)
+    #
+    # You can assign several subjects if you want.
+    #
+    #   class CommentPresenter < Presenter
+    #     subject :comment, :post
+    #     expose :body
+    #     expose :title, :with => :post
+    #   end
+    #
+    #  comment = CommentPresenter.new(Comment.first, Post.first)
+    #
+    # If the :with option specified to one of the subjects, then the default subject is bypassed.
+    # Otherwise, it will be proxied to the default subject.
+    #
+    def initialize(*subjects)
+      self.class.subjects.each_with_index do |name, index|
+        instance_variable_set("@#{name}", subjects[index])
+      end
+    end
+
+    private
+    def proxy_message(subject_name, method)
+      subject_name ||= self.class.subjects.first
+      subject = instance_variable_get("@#{subject_name}")
+      subject = instance_variable_get("@#{self.class.subjects.first}").__send__(subject_name) unless subject || self.class.subjects.include?(subject_name)
+      subject.respond_to?(method) ? subject.__send__(method) : nil
+    end
   end
 end

lib/simple_presenter/namespace.rb

@@ -1,4 +1,6 @@
 module SimplePresenter
   autoload :Base, "simple_presenter/base"
   autoload :Version, "simple_presenter/version"
+
+  require "simple_presenter/rails" if defined?(Rails)
 end

lib/simple_presenter/rails.rb

@@ -0,0 +1,28 @@
+module SimplePresenter
+  class Base
+    private
+    def translate(*args, &block)
+      I18n.t(*args, &block)
+    end
+
+    alias_method :t, :translate
+
+    def localize(*args, &block)
+      I18n.l(*args, &block)
+    end
+
+    alias_method :l, :localize
+
+    def routes
+      Rails.application.routes.url_helpers
+    end
+
+    alias_method :r, :routes
+
+    def helpers
+      ApplicationController.helpers
+    end
+
+    alias_method :h, :helpers
+  end
+end

simple_presenter.gemspec

@@ -9,15 +9,15 @@ Gem::Specification.new do |s|
   s.authors     = ["Nando Vieira"]
   s.email       = ["fnando.vieira@gmail.com"]
   s.homepage    = "http://rubygems.org/gems/simple_presenter"
-  s.summary     = "TODO: Write a description"
+  s.summary     = "A simple presenter/facade/decorator/whatever implementation."
   s.description = s.summary
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]
 
-  # s.add_dependency "activesupport"
   s.add_development_dependency "rake"
   s.add_development_dependency "rspec", "~> 2.7"
+  s.add_development_dependency "pry"
 end

spec/base_spec.rb

@@ -0,0 +1,78 @@
+require "spec_helper"
+
+describe SimplePresenter::Base do
+  describe ".expose" do
+    context "not using :with option" do
+      subject { UserPresenter.new }
+
+      it { should respond_to(:name) }
+      it { should respond_to(:email) }
+      it { should_not respond_to(:password_hash) }
+      it { should_not respond_to(:password_salt) }
+    end
+
+    context "using :with option" do
+      subject { CommentPresenter.new }
+
+      it { should respond_to(:user_name) }
+    end
+  end
+
+  describe ".subjects" do
+    context "using defaults" do
+      let(:user) { stub :name => "John Doe", :email => "john@doe.com" }
+      subject { UserPresenter.new(user) }
+
+      its(:name) { should == "John Doe" }
+      its(:email) { should == "john@doe.com" }
+    end
+
+    context "specifying several subjects" do
+      let(:user) { stub :name => "John Doe" }
+      let(:comment) { stub :body => "Some comment", :user => user }
+      let(:post) { stub :title => "Some post" }
+      subject { CommentPresenter.new(comment, post) }
+
+      its(:body) { should == "Some comment" }
+      its(:post_title) { should == "Some post" }
+      its(:user_name) { should == "John Doe" }
+    end
+
+    context "when subjects are nil" do
+      let(:comment) { stub :body => "Some comment" }
+      subject { CommentPresenter.new(comment, nil) }
+
+      its(:post_title) { should be_nil }
+    end
+  end
+
+  describe ".map" do
+    context "wraps a single subject" do
+      let(:user) { stub :name => "John Doe" }
+      subject { UserPresenter.map([user])[0] }
+
+      it { should be_a(UserPresenter) }
+      its(:name) { should == "John Doe" }
+    end
+
+    context "wraps several subjects" do
+      let(:comment) { stub :body => "Some comment" }
+      let(:post) { stub :title => "Some post" }
+      let(:user) { stub :name => "John Doe" }
+      subject { CommentPresenter.map([comment], post)[0] }
+
+      it { should be_a(CommentPresenter) }
+      its(:body) { should == "Some comment" }
+      its(:post_title) { should == "Some post" }
+    end
+  end
+
+  describe "#initialize" do
+    let(:user) { mock }
+    subject { UserPresenter.new(user) }
+
+    it "assigns the subject" do
+      subject.instance_variable_get("@subject").should == user
+    end
+  end
+end

spec/spec_helper.rb

@@ -4,3 +4,6 @@
 
 require "simple_presenter"
 
+Dir[File.dirname(__FILE__) + "/support/**/*.rb"].each do |file|
+  require file
+end

spec/support/comment.rb

@@ -0,0 +1,7 @@
+class Comment
+  attr_accessor :body, :created_at, :user
+
+  def initialize(attrs = {})
+    attrs.each {|name, value| __send__("#{name}=", value)}
+  end
+end

spec/support/comment_presenter.rb

@@ -0,0 +1,7 @@
+class CommentPresenter < Presenter
+  expose :body
+  expose :name, :with => :user
+  expose :title, :with => :post
+
+  subjects :comment, :post
+end

spec/support/user.rb

@@ -0,0 +1,7 @@
+class User
+  attr_accessor :name, :email, :password_salt, :password_hash
+
+  def initialize(attrs = {})
+    attrs.each {|name, value| __send__("#{name}=", value)}
+  end
+end

spec/support/user_presenter.rb

@@ -0,0 +1,3 @@
+class UserPresenter < Presenter
+  expose :name, :email
+end