Component presenter class

README.md

@@ -46,6 +46,7 @@ app/
       header.css
       header.js
       header.yml
+      header_component.rb # optional
 ```
 
 Keep in mind that you can also use `scss`, `coffeescript`, `haml`, or any other
@@ -60,11 +61,40 @@ coffee-script as long as you have these preprocessors running on your app.
 ```erb
 <!-- app/components/header/_header.html.erb -->
 <div class="header">
-  <h1>This is a header component with the title: <%= properties[:title] %></h1>
-  <h3>And subtitle <%= properties[:subtitle] %></h3>
+  <h1>This is a header component with the title: <%= title %></h1>
+  <h3>And subtitle <%= subtitle %></h3>
+  <% if show_links? %>
+    <ul>
+      <% links.each do |link| %>
+        <li><%= link %></li>
+      <% end %>
+    </ul>
+  <% end %>
 </div>
 ```
 
+```ruby
+# app/components/header/header_component.rb
+class HeaderComponent < MountainView::Presenter
+  properties :title, :subtitle
+  property :links, default: []
+
+  def title
+    properties[:title].titleize
+  end
+
+  def show_links?
+    links.any?
+  end
+end
+```
+
+Including a component class is optional, but it helps avoid polluting your
+views and helpers with presenter logic. Public methods in your component class
+will be made available to the view, along with any properties you define. 
+You can also access all properties using the `properties` method in your 
+component class and views. You can even define property defaults.
+
 ### Using components on your views
 You can then call your components on any view by using the following
 helper:

app/helpers/mountain_view/component_helper.rb

@@ -1,7 +1,8 @@
 module MountainView
   module ComponentHelper
     def render_component(slug, properties = {})
-      render "#{slug}/#{slug}", properties: properties
+      component = MountainView::Presenter.component_for(slug, properties)
+      component.render(controller.view_context)
     end
   end
 end

lib/mountain_view.rb

@@ -1,5 +1,7 @@
 require "mountain_view/version"
 require "mountain_view/configuration"
+require "mountain_view/presenter"
+require "mountain_view/component"
 
 module MountainView
   def self.configuration

lib/mountain_view/engine.rb

@@ -1,5 +1,4 @@
 require "rails"
-require "mountain_view/component"
 
 module MountainView
   class Engine < ::Rails::Engine
@@ -11,6 +10,12 @@ class Engine < ::Rails::Engine
       end
     end
 
+    initializer "mountain_view.load_component_classes",
+                before: :set_autoload_paths do |app|
+      component_paths = "#{MountainView.configuration.components_path}/{*}"
+      app.config.autoload_paths += Dir[component_paths]
+    end
+
     initializer "mountain_view.assets" do |app|
       Rails.application.config.assets.paths <<
         MountainView.configuration.components_path

lib/mountain_view/presenter.rb

@@ -0,0 +1,77 @@
+module MountainView
+  class Presenter
+    class_attribute :_properties, instance_accessor: false
+    self._properties = {}
+
+    attr_reader :slug, :properties
+
+    def initialize(slug, properties = {})
+      @slug = slug
+      @properties = default_properties.deep_merge(properties)
+    end
+
+    def render(context)
+      context.extend ViewContext
+      context.inject_component_context self
+      context.render partial: partial
+    end
+
+    def partial
+      "#{slug}/#{slug}"
+    end
+
+    private
+
+    def default_properties
+      self.class._properties.inject({}) do |sum, (k, v)|
+        sum[k] = v[:default]
+        sum
+      end
+    end
+
+    class << self
+      def component_for(*args)
+        klass = "#{args.first.to_s.camelize}Component".safe_constantize
+        klass ||= self
+        klass.new(*args)
+      end
+
+      def properties(*args)
+        opts = args.extract_options!
+        properties = args.inject({}) do |sum, name|
+          sum[name] = opts
+          sum
+        end
+        define_property_methods(args)
+        self._properties = _properties.merge(properties)
+      end
+      alias_method :property, :properties
+
+      private 
+
+      def define_property_methods(names = [])
+        names.each do |name|
+          next if method_defined?(name) 
+          define_method name do
+            properties[name.to_sym]
+          end
+        end
+      end
+    end
+
+    module ViewContext
+      attr_reader :_component
+      delegate :properties, to: :_component
+
+      def inject_component_context(component)
+        @_component = component
+        protected_methods = MountainView::Presenter.public_methods(false)
+        methods = component.public_methods(false) - protected_methods
+        methods.each do |meth|
+          next if self.class.method_defined?(meth)
+          self.class.delegate meth, to: :_component
+        end
+      end
+    end
+  end
+end

test/dummy/app/components/card/_card.html.erb

@@ -7,11 +7,12 @@
   <% end %>
   <div class="card__content">
     <h3 class="card__content__title">
-      <a href="<%= properties[:link] %>"><%= properties[:title] %></a>
+      <a href="<%= properties[:link] %>"><%= title %></a>
     </h3>
-    <%- if properties[:description] %>
+    <%- if has_description? %>
       <p><%= properties[:description] %></p>
     <%- end %>
+    <p>Location: <%= location %></p>
     <div class="card__content__data">
       <%- if properties[:data] && properties[:data].any? %>
         <%- properties[:data].each do |data| %>
@@ -23,4 +24,4 @@
       <% end %>
     </div>
   </div>
-</div>
+</div>

test/dummy/app/components/card/card.yml

@@ -1,5 +1,6 @@
 -
-  :title: "Aspen Snowmass"
+  :title: "Snowmass"
+  :location: "Aspen"
   :description: "Aspen Snowmass is a winter resort complex located in Pitkin County in western Colorado in the United States. Owned and operated by the Aspen Skiing Company it comprises four skiing/snowboarding areas on four adjacent mountains in the vicinity of the towns of Aspen and Snowmass Village."
   :link: "http://google.com"
   :image_url: "http://i.imgur.com/QzuIJTo.jpg"
@@ -13,7 +14,8 @@
 
 
 -
-  :title: "Breckenridge, Colorado"
+  :title: "Breckenridge"
+  :location: "Colorado"
   :link: "http://facebook.com"
   :image_url: "http://i.imgur.com/w7ZyWPg.jpg"
   :data:

test/dummy/app/components/card/card_component.rb

@@ -0,0 +1,14 @@
+class CardComponent < MountainView::Presenter
+  include ActionView::Helpers::TagHelper
+
+  properties :title, :description, :link, :image_url, :location
+  property :data, default: []
+
+  def title
+    [location, properties[:title]].compact.join(", ")
+  end
+
+  def has_description?
+    description.present?
+  end
+end

test/mountain_view/presenter_test.rb

@@ -0,0 +1,38 @@
+require "test_helper"
+
+class InheritedPresenter < MountainView::Presenter
+  properties :title, :description
+  property :data, default: []
+
+  def title
+    "Foo#{properties[:title].downcase}"
+  end
+end
+
+class MountainView::PresenterTest < ActiveSupport::TestCase
+  test "returns the correct partial path" do
+    presenter = MountainView::Presenter.new("header")
+    assert_equal "header/header", presenter.partial
+  end
+
+  test "exposes properties as provided" do
+    properties = {foo: "bar", hello: "world"}
+    presenter = MountainView::Presenter.new("header", properties)
+    assert_equal properties, presenter.properties
+  end
+
+  test "inherited presenter returns the correct title" do
+    presenter = InheritedPresenter.new("inherited", title: "Bar")
+    assert_equal "Foobar", presenter.title
+  end
+
+  test "inherited presenter responds to #data" do
+    presenter = InheritedPresenter.new("inherited", data: ["Foobar"])
+    assert_equal ["Foobar"], presenter.data
+  end
+
+  test "inherited presenter returns the default value for #data" do
+    presenter = InheritedPresenter.new("inherited", {})
+    assert_equal [], presenter.data
+  end
+end