From 40e2e6d23557b60f9cca02298be742a1b398cb66 Mon Sep 17 00:00:00 2001
From: Steven Soroka <ssoroka78@gmail.com>
Date: Fri, 27 Mar 2009 16:06:56 -0500
Subject: [PATCH] add ignore_nil{} support to rails.  much more flexible than try. closes #2364. [Steven Soroka]

---
 .../lib/active_support/core_ext/object.rb          |    1 +
 .../active_support/core_ext/object/ignore_nil.rb   |   36 ++++++++++++++++++++
 .../test/core_ext/object_and_class_ext_test.rb     |   18 ++++++++++
 3 files changed, 55 insertions(+), 0 deletions(-)
 create mode 100644 activesupport/lib/active_support/core_ext/object/ignore_nil.rb

diff --git a/activesupport/lib/active_support/core_ext/object.rb b/activesupport/lib/active_support/core_ext/object.rb
index 0796a7b..1307316 100644
--- a/activesupport/lib/active_support/core_ext/object.rb
+++ b/activesupport/lib/active_support/core_ext/object.rb
@@ -3,3 +3,4 @@ require 'active_support/core_ext/object/extending'
 require 'active_support/core_ext/object/instance_variables'
 require 'active_support/core_ext/object/metaclass'
 require 'active_support/core_ext/object/misc'
+require 'active_support/core_ext/object/ignore_nil'
\ No newline at end of file
diff --git a/activesupport/lib/active_support/core_ext/object/ignore_nil.rb b/activesupport/lib/active_support/core_ext/object/ignore_nil.rb
new file mode 100644
index 0000000..2932a00
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/object/ignore_nil.rb
@@ -0,0 +1,36 @@
+class Object
+  RESCUE_NIL_EXCEPTIONS = %w(NoMethodError RuntimeError ActionView::TemplateError)
+  RESCUE_NIL_MESSAGES = [/You have a nil object when you didn't expect it/,
+                         /undefined method `.*?' for nil:NilClass/,
+                         /^Called id for nil/]
+  # ignore_nil is actually short for "ignore no method error on nil", referring to the error you get if
+  # you call a method on an object that is unexpectedly nil.  This can happen if you chain method calls
+  # together and one of the methods returns a nil.
+  #
+  # ignore_nil{} will return nil if you get a NoMethodError exception on NilClass.
+  # any other exception type is reraised so that code inside ignore_nil{} blocks don't become a black-
+  # hole.
+  #
+  # ==== Examples
+  #
+  # Without ignore_nil:
+  #   @user && @user.address && @user.address.street
+  # or worse:
+  #   @user.address.street rescue nil
+  # (worse because it catches everything! even if address doesn't have a street method!)
+  #
+  # With ignore_nil:
+  #   ignore_nil { @user.address.street }
+  #
+  def ignore_nil(&block)
+    begin
+      yield
+    rescue Exception => e
+      if RESCUE_NIL_EXCEPTIONS.include?(e.class.name) && RESCUE_NIL_MESSAGES.any?{|exp| e.message =~ exp }
+        return nil
+      else
+        raise e
+      end
+    end
+  end
+end
diff --git a/activesupport/test/core_ext/object_and_class_ext_test.rb b/activesupport/test/core_ext/object_and_class_ext_test.rb
index b6515e0..dfe1479 100644
--- a/activesupport/test/core_ext/object_and_class_ext_test.rb
+++ b/activesupport/test/core_ext/object_and_class_ext_test.rb
@@ -280,3 +280,21 @@ class ObjectTryTest < Test::Unit::TestCase
     assert_equal 'false', false.try(:to_s)
   end
 end
+
+class ObjectIgnoreNilTest < Test::Unit::TestCase
+  def setup
+    @array = [{:a => "test", :b => "hi there"}]
+  end
+
+  def test_ignore_nil_returns_actual_value
+    assert_equal 't', ignore_nil { @array.first[:a].first }
+  end
+  
+  def test_ignore_nil_returns_nil_on_exception
+    assert_equal nil, ignore_nil { @array.first[:c].first }
+  end
+
+  def test_ignore_nil_returns_nil_when_nil
+    assert_equal nil, ignore_nil { @array.first[:c] }
+  end
+end
\ No newline at end of file
-- 
1.5.5