Object#tap for Ruby < 1.8.7

3 files changed, 26 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 3c5f39d321..757cb1da04 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,8 @@
 *2.3.0 [Edge]*
 
+* Object#tap shim for Ruby < 1.8.7. Similar to Object#returning, tap yields self then returns self.  [Jeremy Kemper]
+    array.select { ... }.tap(&:inspect).map { ... }
+
 * TimeWithZone#- gives correct result with wrapped DateTime, and with DateTime argument [Geoff Buesing]
 
 * Updated i18n gem to version 0.1.1 #1635 [Yaroslav Markin]
diff --git a/activesupport/lib/active_support/core_ext/object/misc.rb b/activesupport/lib/active_support/core_ext/object/misc.rb
index 46f9c7d676..4570570bbc 100644
--- a/activesupport/lib/active_support/core_ext/object/misc.rb
+++ b/activesupport/lib/active_support/core_ext/object/misc.rb
@@ -40,6 +40,21 @@ class Object
     value
   end
 
+  # Yields <code>x</code> to the block, and then returns <code>x</code>.
+  # The primary purpose of this method is to "tap into" a method chain,
+  # in order to perform operations on intermediate results within the chain.
+  #
+  #   (1..10).tap { |x| puts "original: #{x.inspect}" }.to_a.
+  #     tap    { |x| puts "array: #{x.inspect}" }.
+  #     select { |x| x%2 == 0 }.
+  #     tap    { |x| puts "evens: #{x.inspect}" }.
+  #     map    { |x| x*x }.
+  #     tap    { |x| puts "squares: #{x.inspect}" }
+  def tap
+    yield self
+    self
+  end unless Object.respond_to?(:tap)
+
   # An elegant way to factor duplication out of options passed to a series of
   # method calls. Each method called in the block, with the block variable as
   # the receiver, will have its options merged with the default +options+ hash
diff --git a/activesupport/test/core_ext/object_ext_test.rb b/activesupport/test/core_ext/object_ext_test.rb
new file mode 100644
index 0000000000..a413d331c4
--- /dev/null
+++ b/activesupport/test/core_ext/object_ext_test.rb
@@ -0,0 +1,8 @@
+require 'abstract_unit'
+
+class ObjectExtTest < Test::Unit::TestCase
+  def test_tap_yields_and_returns_self
+    foo = Object.new
+    assert_equal foo, foo.tap { |x| assert_equal foo, x; :bar }
+  end
+end