Add Object#acts_like? and Time#acts_like_time? and Date#acts_like_date? to facilitate duck-typing

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5951 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 9 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/object/misc.rb b/activesupport/lib/active_support/core_ext/object/misc.rb
index ea8e3a1d6a..aae336e6f4 100644
--- a/activesupport/lib/active_support/core_ext/object/misc.rb
+++ b/activesupport/lib/active_support/core_ext/object/misc.rb
@@ -31,4 +31,13 @@ class Object #:nodoc:
   def to_json
     ActiveSupport::JSON.encode(self)
   end
+
+  # A duck-type assistant method. For example, ActiveSupport extends Date
+  # to define an acts_like_date? method, and extends Time to define
+  # acts_like_time?. As a result, we can do "x.acts_like?(:time)" and
+  # "x.acts_like?(:date)" to do duck-type-safe comparisons, since classes that
+  # we want to act like Time simply need to define an acts_like_time? method.
+  def acts_like?(duck)
+    respond_to? :"acts_like_#{duck}?"
+  end
 end
\ No newline at end of file