From d4e16d760ad84cfb16f047868ffd1a43eb91f3e4 Mon Sep 17 00:00:00 2001
From: Adam Keys <adam@therealadam.com>
Date: Wed, 3 Sep 2008 05:17:15 -0500
Subject: [PATCH] Add injecting to enumerable

---
 .../lib/active_support/core_ext/enumerable.rb      |   25 +++++++++++++++++++-
 activesupport/test/core_ext/enumerable_test.rb     |    5 ++++
 2 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index e451e99..61a9d4e 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -63,7 +63,30 @@ module Enumerable
       inject { |sum, element| sum + element }
     end
   end
-
+  
+  # Syntactic sugar for inject, doesn't require you to return a value from the block parameter
+  #
+  # Injecting is just sugar on top of Ruby's inject. The sugar is in
+  # using the same accumulator reference every time the block is executed, 
+  # rather than requiring you to return the accumulator at the end of your 
+  # block.
+  #
+  # With Ruby's standard inject, this code would fail in a peculiar way:
+  #
+  #   %w(foo bar).injecting({}) { |hsh, str| hsh[str] = str.upcase }
+  #
+  # However with injecting, we'll get something useful:
+  #   
+  #   {'foo' => 'FOO', 'bar' => 'BAR'}
+  #
+  def injecting(accumulator, &block)
+    inject(accumulator) do |accumulator, element|
+      returning accumulator do |accumulator|
+        block.call(accumulator, element)
+      end
+    end
+  end
+  
   # Convert an enumerable to a hash. Examples:
   # 
   #   people.index_by(&:login)
diff --git a/activesupport/test/core_ext/enumerable_test.rb b/activesupport/test/core_ext/enumerable_test.rb
index 2315d8f..2395ada 100644
--- a/activesupport/test/core_ext/enumerable_test.rb
+++ b/activesupport/test/core_ext/enumerable_test.rb
@@ -58,6 +58,11 @@ class EnumerableTests < Test::Unit::TestCase
     assert_equal Payment.new(0), [].sum(Payment.new(0))
   end
 
+  def test_injecting
+    result = %w(foo bar).injecting({}) { |hsh, str| hsh[str] = str.upcase }
+    assert_equal({'foo' => 'FOO', 'bar' => 'BAR'}, result)
+  end
+  
   def test_index_by
     payments = [ Payment.new(5), Payment.new(15), Payment.new(10) ]
     assert_equal({ 5 => payments[0], 15 => payments[1], 10 => payments[2] },
-- 
1.5.5.3