From 03068b2209bb4a43b831766ae3a15f2dcfb5d971 Mon Sep 17 00:00:00 2001
From: Sergio Gil <sgilperez@gmail.com>
Date: Fri, 19 Sep 2008 21:20:26 +0200
Subject: [PATCH] delegate accepts :target and :allow_nil as options

---
 .../active_support/core_ext/module/delegation.rb   |   33 ++++++++++++++++++-
 activesupport/test/core_ext/module_test.rb         |   12 +++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index e0b5f3e..4b5a64b 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -47,16 +47,45 @@ class Module
   #   Foo.new.min # => 4
   #   Foo.new.max # => 11
   #
+  # You can specify a target if you don't want your method to have the same name:
+  #
+  #   class Foo < ActiveRecord::Base
+  #     belongs_to :greeter
+  #     delegate :hi, :to => :greeter, :target => :hello
+  #   end
+  #
+  # If the object in which you delegate can be nil, you may want to use the
+  # :allow_nil option. In that case, it returns nil instead of raising a
+  # NoMethodError exception:
+  #
+  #  class Foo
+  #    def initialize(bar = nil)
+  #      @bar = bar
+  #    end
+  #    delegate :zoo, :to => :bar
+  #  end
+  #  
+  #  Foo.new.zoo   # raises NoMethodError exception (you called nil.zoo)
+  #  
+  #  class Foo
+  #    def initialize(bar = nil)
+  #      @bar = bar
+  #    end
+  #    delegate :zoo, :to => :bar, :allow_nil => true
+  #  end
+  #  
+  #  Foo.new.zoo   # returns nil
+  #
   def delegate(*methods)
     options = methods.pop
     unless options.is_a?(Hash) && to = options[:to]
-      raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
+      raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as an argument (e.g. delegate :hello, :to => :greeter)."
     end
 
     methods.each do |method|
       module_eval(<<-EOS, "(__DELEGATION__)", 1)
         def #{method}(*args, &block)
-          #{to}.__send__(#{method.inspect}, *args, &block)
+          #{to.to_s + ' && ' if options[:allow_nil]}#{to}.__send__(#{(options[:target] || method).inspect}, *args, &block)
         end
       EOS
     end
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index ecdea38..b05a85d 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -84,6 +84,18 @@ class ModuleTest < Test::Unit::TestCase
     assert_raises(ArgumentError) { eval($nowhere) }
     assert_raises(ArgumentError) { eval($noplace) }
   end
+  
+  def test_delegation_with_allow_nil
+    Someone.class_eval { undef :street; delegate :street, :to => :place, :allow_nil => true}
+    david = Someone.new("David")
+    assert_nil david.street
+  end
+  
+  def test_delegation_with_target
+    Someone.class_eval { delegate :town, :to => :place, :target => :city }
+    david = Someone.new("David", Somewhere.new("Paulina", "Chicago"))
+    assert_equal "Chicago", david.town
+  end
 
   def test_parent
     assert_equal Yz::Zy, Yz::Zy::Cd.parent
-- 
1.5.3.7