Association collections have an _ids reader method to match the existing writer for collection_select convenience (e.g. employee.task_ids). The writer method skips blank ids so you can safely do @employee.task_ids = params[:tasks] without checking every time for an empty list or blank values. References #1887, Closes #5780.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5214 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Association collections have an _ids reader method to match the existing writer for collection_select convenience (e.g. employee.task_ids). The writer method skips blank ids so you can safely do @employee.task_ids = params[:tasks] without checking every time for an empty list or blank values.  #1887, #5780 [Michael Schuerig]
+
 * Add an attribute reader method for ActiveRecord::Base.observers [Rick Olson]
 
 * Deprecation: count class method should be called with an options hash rather than two args for conditions and joins.  #6287 [Bob Silva]

activerecord/lib/active_record/associations.rb

@@ -916,8 +916,13 @@ module ActiveRecord
             association
           end
 
+          define_method("#{reflection.name.to_s.singularize}_ids") do
+            send(reflection.name).map(&:id)
+          end
+
           define_method("#{reflection.name.to_s.singularize}_ids=") do |new_value|
-            send("#{reflection.name}=", reflection.class_name.constantize.find(new_value))
+            ids = (new_value || []).reject { |nid| nid.blank? }
+            send("#{reflection.name}=", reflection.class_name.constantize.find(ids))
           end
         end
 

activerecord/test/associations_test.rb

@@ -934,6 +934,10 @@ class HasManyAssociationsTest < Test::Unit::TestCase
     assert firm.clients.include?(Client.find_by_name("New Client"))
   end
   
+  def test_get_ids
+    assert_equal [companies(:first_client).id, companies(:second_client).id], companies(:first_firm).client_ids
+  end
+  
   def test_assign_ids
     firm = Firm.new("name" => "Apple")
     firm.client_ids = [companies(:first_client).id, companies(:second_client).id]
@@ -942,6 +946,16 @@ class HasManyAssociationsTest < Test::Unit::TestCase
     assert_equal 2, firm.clients.length
     assert firm.clients.include?(companies(:second_client))
   end
+
+  def test_assign_ids_ignoring_blanks
+    firm = Firm.new("name" => "Apple")
+    firm.client_ids = [companies(:first_client).id, nil, companies(:second_client).id, '']
+    firm.save
+    firm.reload
+    assert_equal 2, firm.clients.length
+    assert firm.clients.include?(companies(:second_client))
+  end
+
 end
 
 class BelongsToAssociationsTest < Test::Unit::TestCase
@@ -1735,4 +1749,29 @@ class HasAndBelongsToManyAssociationsTest < Test::Unit::TestCase
 
     assert_equal 3, Developer.find(:all, :include => {:projects => :developers}, :conditions => 'developers_projects_join.joined_on IS NOT NULL', :group => group.join(",")).size
   end
+
+  def test_get_ids
+    assert_equal [projects(:active_record).id, projects(:action_controller).id], developers(:david).project_ids
+    assert_equal [projects(:active_record).id], developers(:jamis).project_ids
+  end
+
+  def test_assign_ids
+    developer = Developer.new("name" => "Joe")
+    developer.project_ids = [projects(:active_record).id, projects(:action_controller).id]
+    developer.save
+    developer.reload
+    assert_equal 2, developer.projects.length
+    assert_equal projects(:active_record), developer.projects[0] 
+    assert_equal projects(:action_controller), developer.projects[1] 
+  end
+
+  def test_assign_ids_ignoring_blanks
+    developer = Developer.new("name" => "Joe")
+    developer.project_ids = [projects(:active_record).id, nil, projects(:action_controller).id, '']
+    developer.save
+    developer.reload
+    assert_equal 2, developer.projects.length
+    assert_equal projects(:active_record), developer.projects[0] 
+    assert_equal projects(:action_controller), developer.projects[1] 
+  end
 end