optimize Interpolations::PluralCache to require few object creations

by using the attachment name (symbol) and Class as keys we reduce the number of Strings created before hitting the cache

lib/paperclip/attachment.rb

@@ -68,7 +68,7 @@ module Paperclip
     # +url_generator+ - the object used to generate URLs, using the interpolator. Defaults to Paperclip::UrlGenerator
     # +escape_url+ - Perform URI escaping to URLs. Defaults to true
     def initialize(name, instance, options = {})
-      @name              = name
+      @name              = name.to_sym
       @instance          = instance
 
       options = self.class.default_options.deep_merge(options)

lib/paperclip/interpolations.rb

@@ -90,7 +90,7 @@ module Paperclip
     # all class names. Calling #class will return the expected class.
     def class attachment = nil, style_name = nil
       return super() if attachment.nil? && style_name.nil?
-      plural_cache.underscore_and_pluralize(attachment.instance.class.to_s)
+      plural_cache.underscore_and_pluralize_class(attachment.instance.class)
     end
 
     # Returns the basename of the file. e.g. "file" for "file.jpg"
@@ -186,7 +186,7 @@ module Paperclip
     # Returns the pluralized form of the attachment name. e.g.
     # "avatars" for an attachment of :avatar
     def attachment attachment, style_name
-      plural_cache.pluralize(attachment.name.to_s.downcase)
+      plural_cache.pluralize_symbol(attachment.name)
     end
 
     # Returns the style, or the default style if nil is supplied.

lib/paperclip/interpolations/plural_cache.rb

@@ -2,15 +2,16 @@ module Paperclip
   module Interpolations
     class PluralCache
       def initialize
-        @cache = {}
+        @symbol_cache = {}.compare_by_identity
+        @klass_cache = {}.compare_by_identity
       end
 
-      def pluralize(word)
-        @cache[word] ||= word.pluralize
+      def pluralize_symbol(symbol)
+        @symbol_cache[symbol] ||= symbol.to_s.downcase.pluralize
       end
 
-      def underscore_and_pluralize(word)
-        @cache[word] ||= word.underscore.pluralize
+      def underscore_and_pluralize_class(klass)
+        @klass_cache[klass] ||= klass.name.underscore.pluralize
       end
     end
   end

spec/paperclip/interpolations_spec.rb

@@ -24,9 +24,10 @@ describe Paperclip::Interpolations do
   end
 
   it "returns the class of the instance" do
+    class Thing ; end
     attachment = mock
     attachment.expects(:instance).returns(attachment)
-    attachment.expects(:class).returns("Thing")
+    attachment.expects(:class).returns(Thing)
     assert_equal "things", Paperclip::Interpolations.class(attachment, :style)
   end
 

spec/paperclip/plural_cache_spec.rb

@@ -3,34 +3,35 @@ require 'spec_helper'
 describe 'Plural cache' do
   it 'caches pluralizations' do
     cache = Paperclip::Interpolations::PluralCache.new
-    word = "box"
+    symbol = :box
 
-    word.expects(:pluralize).returns("boxes").once
-
-    cache.pluralize(word)
-    cache.pluralize(word)
+    first = cache.pluralize_symbol(symbol)
+    second = cache.pluralize_symbol(symbol)
+    expect(first).to equal(second)
   end
 
   it 'caches pluralizations and underscores' do
+    class BigBox ; end
     cache = Paperclip::Interpolations::PluralCache.new
-    word = "BigBox"
-
-    word.expects(:pluralize).returns(word).once
-    word.expects(:underscore).returns(word).once
+    klass = BigBox
 
-    cache.underscore_and_pluralize(word)
-    cache.underscore_and_pluralize(word)
+    first = cache.underscore_and_pluralize_class(klass)
+    second = cache.underscore_and_pluralize_class(klass)
+    expect(first).to equal(second)
   end
 
   it 'pluralizes words' do
     cache = Paperclip::Interpolations::PluralCache.new
-    word = "box"
-    assert_equal "boxes", cache.pluralize(word)
+    symbol = :box
+
+    expect(cache.pluralize_symbol(symbol)).to eq("boxes")
   end
 
-  it 'pluralizes and underscore words' do
+  it 'pluralizes and underscore class names' do
+    class BigBox ; end
     cache = Paperclip::Interpolations::PluralCache.new
-    word = "BigBox"
-    assert_equal "big_boxes", cache.underscore_and_pluralize(word)
+    klass = BigBox
+
+    expect(cache.underscore_and_pluralize_class(klass)).to eq("big_boxes")
   end
 end