add recursion feature for validating nested attributes

add tests for nested attributes

spec/fixtures/controllers.rb

@@ -17,4 +17,18 @@ class FakeController < ActionController::Base
   def new
     render text: "new"
   end
+
+    def edit
+        param! :book, Hash, required: true do |b|
+            b.param! :title, String, required: true
+            b.param! :author, Hash do |a|
+                a.param! :first_name, String, required: true
+                a.param! :last_name, String, required: true
+                a.param! :age, Integer, required: true
+            end
+            b.param! :price, BigDecimal, required: true
+        end
+        render text: :book
+    end
+
 end

spec/fixtures/fake_rails_application.rb

@@ -15,6 +15,7 @@ module Rails
         get '/fake/new' => "fake#new"
         get '/fakes' => "fake#index"
         get '/fake/(:id)' => "fake#show"
+          get '/fake/edit' => "fake#edit"
       end
       @routes
     end

spec/rails_integration_spec.rb

@@ -10,6 +10,54 @@ describe FakeController, type: :controller do
     end
   end
 
+  describe "nested_hash" do
+      it "validates nested properties" do
+          params = {
+              'book' => {
+                  'title' => 'One Hundred Years of Solitude',
+                  'author' => {
+                      'first_name' => 'Garbriel Garcia',
+                      'last_name' => 'Marquez',
+                      'age' => '70'
+                  },
+                  'price' => '$1,000.00'
+              }}
+          get :edit, params
+          expect(controller.params[:book][:author][:age]).to eql 70
+          expect(controller.params[:book][:author][:age]).to be_kind_of Integer
+          expect(controller.params[:book][:price]).to eql 1000.0
+          expect(controller.params[:book][:price]).to be_instance_of BigDecimal
+      end
+
+      it "raises error when required nested attribute missing" do
+          params = {
+              'book' => {
+                  'title' => 'One Hundred Years of Solitude',
+                  'author' => {
+                      'last_name' => 'Marquez',
+                      'age' => '70'
+                  },
+                  'price' => '$1,000.00'
+              }}
+          expect { get :edit, params }.to raise_error { |error|
+              expect(error).to be_a(RailsParam::Param::InvalidParameterError)
+              expect(error.param).to eql("first_name")
+              expect(error.options).to eql({ :required => true })
+          }
+      end
+
+      it "passes when hash that's not required but has required attributes is missing" do
+          params = {
+              'book' => {
+                  'title' => 'One Hundred Years of Solitude',
+                  'price' => '$1,000.00'
+              }}
+          get :edit, params
+          expect(controller.params[:book][:price]).to eql 1000.0
+          expect(controller.params[:book][:price]).to be_instance_of BigDecimal
+      end
+  end
+
   describe "InvalidParameterError" do
     it "raises an exception with params attributes" do
       expect { get :index, sort: "foo" }.to raise_error { |error|