lib/arc-furnace/unfold.rb in arc-furnace-0.1.3 vs lib/arc-furnace/unfold.rb in arc-furnace-0.1.4

@@ -5,28 +5,30 @@
 # rows and whatnot. Only #unfold is required for implementation.
 module ArcFurnace
   class Unfold < Source
 
     private_attr_reader :source, :unfolded
-    attr_reader :value
 
     def initialize(source:)
       @source = source
-      advance
+      @value = nil
     end
 
-    def prepare
-      source.prepare
+    def value
+      if @value.nil? && !empty?
+        advance
+      end
+      @value
     end
 
     # Given a row from the source, produce the unfolded rows as a result. This method must return
     # an array.
     def unfold(row)
       raise "Unimplemented!"
     end
 
     def empty?
-      value.nil? && source.empty?
+      @value.nil? && source.empty?
     end
 
     def advance
       while (unfolded.nil? || unfolded.empty?) && !source.empty?
         # Use reverse since we want to process in-order, but, #pop is much faster than #unshift