Base#==, eql?, and hash methods. == returns true if its argument is identical to self or if it's an instance of the same class, is not new?, and has the same id. eql? is an alias for ==. hash delegates to id.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5773 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 61 insertions, 0 deletions

diff --git a/activeresource/CHANGELOG b/activeresource/CHANGELOG
index 1079156fdc..a9bb625781 100644
--- a/activeresource/CHANGELOG
+++ b/activeresource/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Base#==, eql?, and hash methods. == returns true if its argument is identical to self or if it's an instance of the same class, is not new?, and has the same id. eql? is an alias for ==. hash delegates to id.  [Jeremy Kemper]
+
 * Allow subclassed resources to share the site info [Rick, Jeremy Kemper]
 
     class BeastResource < ActiveResource::Base
diff --git a/activeresource/lib/active_resource/base.rb b/activeresource/lib/active_resource/base.rb
index 9a810e4adf..a8918b1eee 100644
--- a/activeresource/lib/active_resource/base.rb
+++ b/activeresource/lib/active_resource/base.rb
@@ -111,6 +111,22 @@ module ActiveResource
       attributes[self.class.primary_key] = id
     end
 
+    # True if and only if +other+ is the same object or is an instance of the same class, is not new?, and has the same id.
+    def ==(other)
+      other.equal?(self) || (other.instance_of?(self.class) && !other.new? && other.id == id)
+    end
+
+    # Delegates to ==
+    def eql?(other)
+      self == other
+    end
+
+    # Delegates to id in order to allow two resources of the same type and id to work with something like:
+    #   [Person.find(1), Person.find(2)] & [Person.find(1), Person.find(4)] # => [Person.find(1)]
+    def hash
+      id.hash
+    end
+
     def save
       new? ? create : update
     end
diff --git a/activeresource/test/base/equality_test.rb b/activeresource/test/base/equality_test.rb
new file mode 100644
index 0000000000..4a3f75f998
--- /dev/null
+++ b/activeresource/test/base/equality_test.rb
@@ -0,0 +1,43 @@
+require "#{File.dirname(__FILE__)}/../abstract_unit"
+require "fixtures/person"
+require "fixtures/street_address"
+
+class BaseEqualityTest < Test::Unit::TestCase
+  def setup
+    @new = Person.new
+    @one = Person.new(:id => 1)
+    @two = Person.new(:id => 2)
+    @street = StreetAddress.new(:id => 2)
+  end
+
+  def test_should_equal_self
+    assert @new == @new, '@new == @new'
+    assert @one == @one, '@one == @one'
+  end
+
+  def test_shouldnt_equal_new_resource
+    assert @new != @one, '@new != @one'
+    assert @one != @new, '@one != @new'
+  end
+
+  def test_shouldnt_equal_different_class
+    assert @two != @street, 'person != street_address with same id'
+    assert @street != @two, 'street_address != person with same id'
+  end
+
+  def test_eql_should_alias_equals_operator
+    assert_equal @new == @new, @new.eql?(@new)
+    assert_equal @new == @one, @new.eql?(@one)
+
+    assert_equal @one == @one, @one.eql?(@one)
+    assert_equal @one == @new, @one.eql?(@new)
+
+    assert_equal @one == @street, @one.eql?(@street)
+  end
+
+  def test_hash_should_be_id_hash
+    [@new, @one, @two, @street].each do |resource|
+      assert_equal resource.id.hash, resource.hash
+    end
+  end
+end