collections : add support for enum chains

lib/saxlsx/rows_collection.rb

@@ -12,7 +12,11 @@ def initialize(index, file_system, workbook)
     end
 
     def each(&block)
-      RowsCollectionParser.parse @index, @sheet, @workbook, &block
+      if block
+        RowsCollectionParser.parse @index, @sheet, @workbook, &block
+      else
+        to_enum
+      end
     end
 
     def count

lib/saxlsx/shared_string_collection.rb

@@ -9,7 +9,11 @@ def initialize(file_system)
     end
 
     def each(&block)
-      SharedStringCollectionParser.parse @file_system, &block
+      if block
+        SharedStringCollectionParser.parse @file_system, &block
+      else
+        to_enum
+      end
     end
 
   end

lib/saxlsx/sheet_collection.rb

@@ -10,7 +10,11 @@ def initialize(file_system, workbook)
     end
 
     def each(&block)
-      SheetCollectionParser.parse @file_system, @workbook, &block
+      if block
+        SheetCollectionParser.parse @file_system, @workbook, &block
+      else
+        to_enum
+      end
     end
 
   end

lib/saxlsx/style_collection.rb

@@ -9,7 +9,11 @@ def initialize(file_system)
     end
 
     def each(&block)
-      StyleCollectionParser.parse @file_system, &block
+      if block
+        StyleCollectionParser.parse @file_system, &block
+      else
+        to_enum
+      end
     end
 
   end

spec/sheet_spec.rb

@@ -27,6 +27,16 @@
     end
   end
 
+  it 'handle enumeration' do
+    indexes = []
+    Workbook.open filename do |w|
+      w.sheets[0].rows.each.with_index do |r, i|
+        indexes << i
+      end
+    end
+    indexes.should eq [0, 1, 2, 3, 4, 5, 6]
+  end
+
   it 'Rows content' do
     Workbook.open filename do |w|
       w.sheets[0].tap do |s|