Component presenter class

README.md

@@ -44,6 +44,7 @@ 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
@@ -58,11 +59,33 @@ 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>
+  <ul>
+    <% links.each do |link| %>
+      <li><%= link %></li>
+    <% end %>
+  </ul>
 </div>
 ```
 
+```ruby
+# app/components/header/header_component.rb
+class HeaderComponent < MountainView::Presenter
+  attributes :title, :subtitle
+  attribute :links, default: []
+
+  def title
+    properties[:title].titleize
+  end
+end
+```
+
+Including a component class is optional, but it helps avoid polluting your
+views and helpers with presenter logic. Any properties you pass when rendering
+the component will also be exposed to the view as local variables, and you can
+access them using the `properties` method in your component class and views.
+
 ### 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)
+      render partial: component.partial, locals: component.locals
     end
   end
 end

lib/mountain_view.rb

@@ -1,5 +1,6 @@
 require "mountain_view/version"
 require "mountain_view/configuration"
+require "mountain_view/presenter"
 
 module MountainView
   def self.configuration

lib/mountain_view/presenter.rb

@@ -0,0 +1,64 @@
+module MountainView
+  class Presenter
+    class_attribute :_attributes, instance_accessor: false
+    self._attributes = {}
+
+    attr_reader :slug, :properties
+    alias_method :props, :properties
+
+    def initialize(slug, properties={})
+      @slug = slug
+      @properties = properties
+    end
+
+    def partial
+      "#{slug}/#{slug}"
+    end
+
+    def locals
+      locals = build_hash
+      locals.merge(properties: locals)
+    end
+
+    def attributes
+      @attributes ||= properties.keys.inject({}) do |sum, name|
+        sum[name] = {}
+        sum
+      end.merge(self.class._attributes)
+    end
+
+    private
+
+    def build_hash
+      attributes.inject({}) do|sum, (k, v)|
+        sum[k] = attribute_value(k)
+        sum
+      end
+    end
+
+    def attribute_value(key)
+      attribute = attributes[key] || return
+      value = respond_to?(key) ? send(key) : properties[key]
+      value || attribute[:default]
+    end
+
+    class << self
+      def attributes(*args)
+        opts = args.extract_options!
+        attributes = args.inject({}) do |sum, name|
+          sum[name] = opts
+          sum
+        end
+        self._attributes = self._attributes.merge(attributes)
+      end
+
+      alias_method :attribute, :attributes
+    end
+
+    def self.component_for(slug, properties={})
+      klass = descendants.find{|d| d.to_s.demodulize == "#{slug.to_s.classify}Component" }
+      klass ||= self
+      klass.new(slug, properties)
+    end
+  end
+end

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

@@ -12,6 +12,7 @@
     <%- if properties[:description] %>
       <p><%= properties[:description] %></p>
     <%- end %>
+    <%= foobar %>
     <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_component.rb

@@ -0,0 +1,19 @@
+class CardComponent < MountainView::Presenter
+  attributes :title, :description, :link, :image_url
+  attribute :data, default: []
+  attribute :foobar
+
+  def title
+    ['Foobar', properties[:title]].join(' - ')
+  end
+
+  def foobar
+    h.content_tag(:p, "Foobar!!")
+  end
+
+  private
+
+  def h
+    ActionController::Base.helpers
+  end
+end

test/dummy/config/initializers/mountain_view.rb

@@ -1,3 +1,6 @@
 MountainView.configure do |config|
   config.included_stylesheets = ["global"]
 end
+
+# include component classes
+Dir.glob('app/components/**/*.rb') { |f| require_relative "../../#{f}" }

test/mountain_view/presenter_test.rb

@@ -0,0 +1,48 @@
+require "test_helper"
+class InheritedPresenter < MountainView::Presenter
+  attributes :title, :description
+  attribute :data, default: []
+
+  def title
+    "Foo#{properties[:title].downcase}"
+  end
+end
+
+class MountainViewPresenterTest < ActiveSupport::TestCase
+  def test_partial
+    presenter = MountainView::Presenter.new("header")
+    assert_equal "header/header", presenter.partial
+  end
+
+  def test_locals
+    properties = {name: 'Foo', title: 'Bar'}
+    presenter = MountainView::Presenter.new('header', properties)
+    assert_equal add_properties(properties), presenter.locals
+  end
+
+  def test_attributes
+    properties = {name: 'Foo', title: 'Bar'}
+    presenter = MountainView::Presenter.new('header', properties)
+    assert_equal({name: {}, title: {}}, presenter.attributes)
+  end
+
+  def test_inherited_locals
+    properties = {name: 'Foo', title: 'Bar'}
+    presenter = InheritedPresenter.new('header', properties)
+    presenter_properties = {title: 'Foobar', description: nil, data: []}
+    expected_properties = properties.merge(presenter_properties)
+    assert_equal add_properties(expected_properties), presenter.locals
+  end
+
+  def test_inherited_attributes
+    properties = {name: 'Foo', title: 'Bar'}
+    presenter = InheritedPresenter.new('header', properties)
+    presenter_attributes = {title: {}, description: {}, data: {default: []}}
+    expected_attributes = {name: {}, title: {}}.merge(presenter_attributes)
+    assert_equal expected_attributes, presenter.attributes
+  end
+
+  def add_properties(properties)
+    properties.merge(properties: properties)
+  end
+end