Allow presenters to define initialize via inheritance

lib/shortcode/presenter.rb

@@ -7,9 +7,7 @@ def self.register(configuration, presenter)
 
   def self.validate(presenter)
     raise ArgumentError, "The presenter must define the class method #for" unless presenter.respond_to?(:for)
-    unless presenter.private_instance_methods(false).include?(:initialize)
-      raise ArgumentError, "The presenter must define an initialize method"
-    end
+    raise ArgumentError, "The presenter must define an initialize method" unless init_defined?(presenter)
 
     %w[content attributes].each do |method|
       unless presenter.method_defined?(method.to_sym)
@@ -18,6 +16,12 @@ def self.validate(presenter)
     end
   end
 
+  def self.init_defined?(presenter)
+    return false if presenter == Object
+
+    presenter.private_instance_methods(false).include?(:initialize) || init_defined?(presenter.superclass)
+  end
+
   def initialize(name, configuration, attributes, content, additional_attributes)
     @configuration = configuration
     @attributes = attributes

spec/shortcode/presenter_spec.rb

@@ -7,6 +7,8 @@
 require "support/presenters/multiple_presenter"
 require "support/presenters/missing_for_presenter"
 require "support/presenters/missing_initialize_presenter"
+require "support/presenters/child_presenter"
+require "support/presenters/child_missing_initialize_presenter"
 require "support/presenters/missing_content_presenter"
 require "support/presenters/missing_attributes_presenter"
 
@@ -101,6 +103,20 @@
       end
     end
 
+    context "when initialize exists on non-Object ancestor class" do
+      it "does not raise an exception" do
+        expect { shortcode.register_presenter ChildPresenter }
+          .not_to raise_error
+      end
+    end
+
+    context "when self and ancestory are missing #initialize method" do
+      it "raises an exception" do
+        expect { shortcode.register_presenter ChildMissingInitializePresenter }
+          .to raise_error(ArgumentError, "The presenter must define an initialize method")
+      end
+    end
+
     context "when missing #content method" do
       it "raises an exception" do
         expect { shortcode.register_presenter MissingContentPresenter }

spec/support/presenters/child_missing_initialize_presenter.rb

@@ -0,0 +1,11 @@
+require "support/presenters/parent_missing_initialize_presenter"
+
+class ChildMissingInitializePresenter < ParentMissingInitializePresenter
+
+  def self.for; end
+
+  def content; end
+
+  def attributes; end
+
+end

spec/support/presenters/child_presenter.rb

@@ -0,0 +1,11 @@
+require "support/presenters/parent_presenter"
+
+class ChildPresenter < ParentPresenter
+
+  def self.for; end
+
+  def content; end
+
+  def attributes; end
+
+end

spec/support/presenters/parent_missing_initialize_presenter.rb

@@ -0,0 +1,2 @@
+class ParentMissingInitializePresenter
+end

spec/support/presenters/parent_presenter.rb

@@ -0,0 +1,5 @@
+class ParentPresenter
+
+  def initialize; end
+
+end