Add value_humanizer to i18n-ize header values

lib/comma/extractors.rb

@@ -1,3 +1,5 @@
+require 'active_support/core_ext/class/attribute'
+
 module Comma
 
   class Extractor
@@ -27,18 +29,26 @@ def convert_to_data_value(result)
 
   class HeaderExtractor < Extractor
 
+    class_attribute :value_humanizer
+
+    DEFAULT_VALUE_HUMANIZER = lambda do |value, model_class|
+      value.is_a?(String) ? value : value.to_s.humanize
+    end
+    self.value_humanizer = DEFAULT_VALUE_HUMANIZER
+
     def method_missing(sym, *args, &block)
-      @results << sym.to_s.humanize if args.blank?
+      model_class = @instance.class
+      @results << self.value_humanizer.call(sym, model_class) if args.blank?
       args.each do |arg|
         case arg
         when Hash
           arg.each do |k, v|
-            @results << ((v.is_a? String) ? v : v.to_s.humanize)
+            @results << self.value_humanizer.call(v, get_association_class(model_class, sym))
           end
         when Symbol
-          @results << arg.to_s.humanize
+          @results << self.value_humanizer.call(arg, get_association_class(model_class, sym))
         when String
-          @results << arg
+          @results << self.value_humanizer.call(arg, model_class)
         else
           raise "Unknown header symbol #{arg.inspect}"
         end
@@ -48,6 +58,13 @@ def method_missing(sym, *args, &block)
     def __static_column__(header = '', &block)
       @results << header
     end
+
+    private
+
+    def get_association_class(model_class, association)
+      model_class.respond_to?(:reflect_on_association) ?
+        model_class.reflect_on_association(arg).klass : nil
+    end
   end
 
   class DataExtractor < Extractor

spec/comma/rails/active_record_spec.rb

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 require 'spec_helper'
 
 describe Comma, 'generating CSV from an ActiveRecord object' do
@@ -35,4 +36,34 @@ class Person < ActiveRecord::Base
       Person.teenagers.to_comma
     end
   end
+
+  describe 'with custom value_humanizer' do
+    before do
+      Comma::HeaderExtractor.value_humanizer =
+        lambda do |value, model_class|
+          if model_class.respond_to?(:human_attribute_name)
+            model_class.human_attribute_name(value)
+          else
+            value.is_a?(String) ? value : value.to_s.humanize
+          end
+        end
+
+      I18n.config.backend.store_translations(:ja, {:activerecord => {:attributes => {:person => {:age => '年齢', :name => '名前'}}}})
+      @original_locale = I18n.locale
+      I18n.locale = :ja
+
+      Person.create(:age => 19, :name => 'John')
+    end
+
+    after do
+      I18n.locale = @original_locale
+
+      Comma::HeaderExtractor.value_humanizer =
+        Comma::HeaderExtractor::DEFAULT_VALUE_HUMANIZER
+    end
+
+    it 'should i18n-ize header values' do
+      Person.teenagers.to_comma.should match(/^名前,年齢/)
+    end
+  end
 end