add default_option_type_name and default_unit

app/models/spree/size_chart.rb

@@ -76,6 +76,16 @@ def hash_size_values
     def option_type_with_unit
       "#{option_type.try(:presentation)} (#{unit})"
     end
+
+    def default_or_selected_option_type
+      option_type || Spree::OptionType.where(["lower(name) = ?", default_option_type_name.downcase]).first
+    end
+
+    def default_or_selected_unit
+      unit || default_unit
+    end
+
+    delegate :default_option_type_name, :default_unit, :to => SpreeSizeChart
   end
 
 end

app/views/spree/admin/size_charts/edit.html.erb

@@ -11,7 +11,7 @@
 
   <%= f.field_container :option_type_id do %>
     <%= f.label :option_type_id, t(:option_type_id) %>
-    <%= f.select :option_type_id, Spree::OptionType.select("id, name").map {|opt| [opt.name, opt.id] }, { :include_blank => true } %>
+    <%= f.collection_select :option_type_id, Spree::OptionType.all, :id, :name, :selected => @size_chart.default_or_selected_option_type.try(:id)  %>
   <% end %>
 
   <%= f.field_container :prototype_id do %>
@@ -21,7 +21,7 @@
 
   <%= f.field_container :unit do %>
     <%= f.label :unit %>
-    <%= f.select :unit, Spree::SizeChart::UNITS, :include_blank => true %>
+    <%= f.select :unit, Spree::SizeChart::UNITS, :selected => @size_chart.default_or_selected_unit, :include_blank => true %>
   <% end %>
 
   <%= f.field_container :size_types do %>

lib/spree_size_chart/engine.rb

@@ -1,4 +1,8 @@
 module SpreeSizeChart
+  mattr_accessor :default_option_type_name, :default_unit
+  @@default_option_type_name = 'size'
+  @@default_unit = 'cm'
+
   class Engine < Rails::Engine
     engine_name 'spree_size_chart'
 

spec/requests/spree_size_chart_spec.rb

@@ -140,4 +140,14 @@ def fill_size_chart
     end
   end
 
+  scenario 'default option type name' do
+    SpreeSizeChart.default_option_type_name = 'color'
+    @color = FactoryGirl.create(:option_type, :name => "color", :presentation => 'Color')
+
+    visit spree.edit_admin_product_path(@product)
+    click_link "Size Chart"
+    page.should have_content('Edit')
+    find_field('size_chart_option_type_id').value.to_i.should == @color.id
+    SpreeSizeChart.default_option_type_name = 'size'
+  end
 end