Merge pull request #282 from Shopify/load_slice

allow drops to optimize loading a slice of elements

lib/liquid/htmltags.rb

@@ -23,7 +23,7 @@ module Liquid
       from = @attributes['offset'] ? context[@attributes['offset']].to_i : 0
       to = @attributes['limit'] ? from + context[@attributes['limit']].to_i : nil
 
-      collection = Utils.slice_collection_using_each(collection, from, to)
+      collection = Utils.slice_collection(collection, from, to)
 
       length = collection.length
 

lib/liquid/tags/for.rb

@@ -75,8 +75,7 @@ module Liquid
       limit = context[@attributes['limit']]
       to    = limit ? limit.to_i + from : nil
 
-
-      segment = Utils.slice_collection_using_each(collection, from, to)
+      segment = Utils.slice_collection(collection, from, to)
 
       return render_else(context) if segment.empty?
 

lib/liquid/utils.rb

@@ -1,5 +1,18 @@
 module Liquid
   module Utils
+
+    def self.slice_collection(collection, from, to)
+      if (from != 0 || to != nil) && collection.respond_to?(:load_slice)
+        collection.load_slice(from, to)
+      else
+        slice_collection_using_each(collection, from, to)
+      end
+    end
+
+    def self.non_blank_string?(collection)
+      collection.is_a?(String) && collection != ''
+    end
+
     def self.slice_collection_using_each(collection, from, to)
       segments = []
       index = 0
@@ -22,9 +35,5 @@ module Liquid
 
       segments
     end
-
-    def self.non_blank_string?(collection)
-      collection.is_a?(String) && collection != ''
-    end
   end
 end