Merge pull request #85 from michaelfairley/decorate_associations

Automatically decorate associations with decorates_association

lib/draper/base.rb

@@ -53,6 +53,32 @@ module Draper
       define_method(input){ @model }
     end
 
+    # Typically called withing a decorator definition, this method causes
+    # the assocation to be decorated when it is retrieved.
+    #
+    # @param [Symbol] name of association to decorate, like `:products`
+    # @option opts [Class] :with The decorator to decorate the association with
+    def self.decorates_association(association_symbol, options = {})
+      define_method(association_symbol) do
+        orig_association = model.send(association_symbol)
+        return orig_association  if orig_association.nil?
+        if options[:with]
+          options[:with].decorate(orig_association)
+        else
+          reflection = model.class.reflect_on_association(association_symbol)
+          "#{reflection.klass}Decorator".constantize.decorate(orig_association)
+        end
+      end
+    end
+
+    # A convenience method for decorating multiple associations. Calls
+    # decorates_association on each of the given symbols.
+    #
+    # @param [Symbols*] name of associations to decorate
+    def self.decorates_associations(*association_symbols)
+      association_symbols.each{ |sym| decorates_association(sym) }
+    end
+
     # Specifies a black list of methods which may *not* be proxied to
     # to the wrapped object.
     #

spec/draper/base_spec.rb

@@ -74,6 +74,44 @@ describe Draper::Base do
     end
   end
 
+  context(".decorates_association") do
+    context "for collection associations" do
+      before(:each){ subject.class_eval{ decorates_association :similar_products } }
+      it "causes the association's method to return a collection of wrapped objects" do
+        subject.similar_products.each{ |decorated| decorated.should be_instance_of(ProductDecorator) }
+      end
+    end
+
+    context "for a singular association" do
+      before(:each){ subject.class_eval{ decorates_association :previous_version } }
+      it "causes the association's method to return a single wrapped object if the association is singular" do
+        subject.previous_version.should be_instance_of(ProductDecorator)
+      end
+
+      it "causes the association's method to return nil if the association is nil" do
+        source.stub(:previous_version){ nil }
+        subject.previous_version.should be_nil
+      end
+    end
+
+    context "with a specific decorator specified" do
+      before(:each){ subject.class_eval{ decorates_association :previous_version, :with => SpecificProductDecorator } }
+      it "causes the association to be decorated with the specified association" do
+        subject.previous_version.should be_instance_of(SpecificProductDecorator)
+      end
+    end
+  end
+
+  context('.decorates_associations') do
+    subject { Decorator }
+    it "decorates each of the associations" do
+      subject.should_receive(:decorates_association).with(:similar_products)
+      subject.should_receive(:decorates_association).with(:previous_version)
+
+      subject.decorates_associations :similar_products, :previous_version
+    end
+  end
+
   context(".model / .to_model") do
     it "should return the wrapped object" do
       subject.to_model.should == source

spec/spec_helper.rb

@@ -13,5 +13,6 @@ require './spec/support/samples/namespaced_product.rb'
 require './spec/support/samples/namespaced_product_decorator.rb'
 require './spec/support/samples/product.rb'
 require './spec/support/samples/product_decorator.rb'
+require './spec/support/samples/specific_product_decorator.rb'
 require './spec/support/samples/widget.rb'
 require './spec/support/samples/widget_decorator.rb'

spec/support/samples/product.rb

@@ -44,4 +44,16 @@ class Product < ActiveRecord::Base
   def block
     yield
   end
+
+  def self.reflect_on_association(association_symbol)
+    OpenStruct.new(:klass => self)
+  end
+
+  def similar_products
+    [Product.new, Product.new]
+  end
+
+  def previous_version
+    Product.new
+  end
 end

spec/support/samples/specific_product_decorator.rb

@@ -0,0 +1,4 @@
+require './spec/support/samples/product_decorator'
+
+class SpecificProductDecorator < ProductDecorator
+end