diff --git a/app/models/add_friend.rb b/app/models/add_friend.rb
index 6ebd8c4..a84639d 100644
--- a/app/models/add_friend.rb
+++ b/app/models/add_friend.rb
@@ -14,8 +14,8 @@ class AddFriend < Task
   alias :friend :target
   alias :friend= :target=
 
-  validate :requestor_is_person
-  validate :target_is_person
+	validates :requestor, :kind_of => { :kind => Person }
+	validates :target, :kind_of => { :kind => Person }
 
   after_create do |task|
     TaskMailer.invitation_notification(task).deliver unless task.friend
@@ -27,18 +27,6 @@ class AddFriend < Task
     requestor.add_friend(target, group_for_person)
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:add_friend, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_person
-    unless target.person?
-      errors.add(:add_friend, N_('Target must be a person.'))
-    end
-  end
-
   def permission
     :manage_friends
   end
diff --git a/app/models/add_member.rb b/app/models/add_member.rb
index 8f5ca13..4b887e6 100644
--- a/app/models/add_member.rb
+++ b/app/models/add_member.rb
@@ -2,8 +2,8 @@ class AddMember < Task
 
   validates_presence_of :requestor_id, :target_id
 
-  validate :requestor_is_person
-  validate :target_is_organization
+  validates :requestor, kind_of: {kind: Person}
+  validates :target, kind_of: {kind: Organization}
 
   alias :person :requestor
   alias :person= :requestor=
@@ -58,16 +58,4 @@ class AddMember < Task
     suggestion.disable if suggestion
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:add_member, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_organization
-    unless target.organization?
-      errors.add(:add_member, N_('Target must be an organization.'))
-    end
-  end
-
 end
diff --git a/app/models/approve_article.rb b/app/models/approve_article.rb
index 02dc104..f2f8a9f 100644
--- a/app/models/approve_article.rb
+++ b/app/models/approve_article.rb
@@ -1,14 +1,14 @@
 class ApproveArticle < Task
   validates_presence_of :requestor_id, :target_id
 
-  validate :requestor_is_person
-  validate :target_is_organization
-  validate :request_is_member_of_target
+  validates :requestor, kind_of: {kind: Person}
+  #validates :target, kind_of: {kind: Organization}
+  #validate :request_is_member_of_target
 
   def article_title
     article ? article.title : _('(The original text was removed)')
   end
-  
+
   def article
     Article.find_by_id data[:article_id]
   end
@@ -132,20 +132,8 @@ class ApproveArticle < Task
     message
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:approve_article, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_organization
-    unless target.organization?
-      errors.add(:approve_article, N_('Target must be an organization.'))
-    end
-  end
-
   def request_is_member_of_target
-    unless requestor.is_member_of?(target) 
+    unless requestor.is_member_of?(target)
       errors.add(:approve_article, N_('Requestor must be a member of target.'))
     end
   end
diff --git a/app/models/change_password.rb b/app/models/change_password.rb
index b0d380a..9d1a1dd 100644
--- a/app/models/change_password.rb
+++ b/app/models/change_password.rb
@@ -18,7 +18,7 @@ class ChangePassword < Task
 
   validates_presence_of :requestor
 
-  validate :requestor_is_person
+  validates :requestor, kind_of: {kind: Person}
 
   ###################################################
   # validations for updating a ChangePassword task 
@@ -74,9 +74,4 @@ class ChangePassword < Task
     end
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:change_password, N_('Requestor must be a person.'))
-    end
-  end
 end
diff --git a/app/models/create_community.rb b/app/models/create_community.rb
index 96f5539..91df0f3 100644
--- a/app/models/create_community.rb
+++ b/app/models/create_community.rb
@@ -3,8 +3,8 @@ class CreateCommunity < Task
   validates_presence_of :requestor_id, :target_id
   validates_presence_of :name
 
-  validate :requestor_is_person
-  validate :target_is_environment
+  validates :requestor, kind_of: {kind: Person}
+  validates :target, kind_of: {kind: Environment}
 
   alias :environment :target
   alias :environment= :target=
@@ -95,16 +95,4 @@ class CreateCommunity < Task
     _('Your request for registering the community "%{community}" was approved. You can access %{environment} now and start using your new community.') % { :community => self.name, :environment => self.environment }
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:create_community, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_environment
-    unless target.class == Environment
-      errors.add(:create_community, N_('Target must be an environment.'))
-    end
-  end
-
 end
diff --git a/app/models/create_enterprise.rb b/app/models/create_enterprise.rb
index 6184216..0c56d66 100644
--- a/app/models/create_enterprise.rb
+++ b/app/models/create_enterprise.rb
@@ -27,8 +27,7 @@ class CreateEnterprise < Task
   # checks for actual attributes
   validates_presence_of :requestor_id, :target_id
 
-  validate :requestor_is_person
-  validate :target_is_environment
+  validates :requestor, kind_of: {kind: Person}
 
   # checks for admins required attributes
   DATA_FIELDS.each do |attribute|
@@ -217,16 +216,4 @@ class CreateEnterprise < Task
     :validate_enterprise
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:create_enterprise, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_environment
-    unless target.class == Environment
-      errors.add(:create_enterprise, N_('Target must be an environment.'))
-    end
-  end
-
 end
diff --git a/app/models/email_activation.rb b/app/models/email_activation.rb
index 0ed18cb..82cdee8 100644
--- a/app/models/email_activation.rb
+++ b/app/models/email_activation.rb
@@ -2,8 +2,8 @@ class EmailActivation < Task
 
   validates_presence_of :requestor_id, :target_id
 
-  validate :requestor_is_person
-  validate :target_is_environment
+  validates :requestor, kind_of: {kind: Person}
+  validates :target, kind_of: {kind: Environment}
 
   validate :already_requested, :on => :create
 
@@ -11,10 +11,8 @@ class EmailActivation < Task
   alias :person :requestor
 
   def already_requested
-    if self.requestor.person?
-      if !self.requestor.nil? && self.requestor.user.email_activation_pending?
-        self.errors.add(:base, _('You have already requested activation of your mailbox.'))
-      end
+    if !self.requestor.nil? && self.requestor.person? && self.requestor.user.email_activation_pending?
+      self.errors.add(:base, _('You have already requested activation of your mailbox.'))
     end
   end
 
@@ -47,16 +45,4 @@ class EmailActivation < Task
     false
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:email_activation, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_environment
-    unless target.class == Environment
-      errors.add(:email_activation, N_('Target must be an environment.'))
-    end
-  end
-
 end
diff --git a/app/models/enterprise_activation.rb b/app/models/enterprise_activation.rb
index 96739d0..484f054 100644
--- a/app/models/enterprise_activation.rb
+++ b/app/models/enterprise_activation.rb
@@ -8,8 +8,7 @@ class EnterpriseActivation < Task
 
   validates_presence_of :enterprise
 
-  validate :requestor_is_person
-  validate :target_is_enterprise
+  validates :target, kind_of: {kind: Enterprise}
 
   def perform
     self.enterprise.enable self.requestor
@@ -47,16 +46,4 @@ class EnterpriseActivation < Task
     end
   end
 
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:enterprise_activation, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_enterprise
-    unless target.enterprise?
-      errors.add(:enterprise_activation, N_('Target must be an enterprise.'))
-    end
-  end
-
 end
diff --git a/app/models/invitation.rb b/app/models/invitation.rb
index 2eae3d8..375562c 100644
--- a/app/models/invitation.rb
+++ b/app/models/invitation.rb
@@ -6,8 +6,7 @@ class Invitation < Task
 
   validates_presence_of :target_id, :if => Proc.new{|invite| invite.friend_email.blank?}
 
-  validate :requestor_is_person
-  validate :target_is_person
+  validates :requestor, kind_of: {kind: Person}
 
   validates_presence_of :friend_email, :if => Proc.new{|invite| invite.target_id.blank?}
   validates_format_of :friend_email, :with => Noosfero::Constants::EMAIL_FORMAT, :if => Proc.new{|invite| invite.target_id.blank?}
@@ -37,11 +36,9 @@ class Invitation < Task
   end
 
   def not_invite_yourself
-    if friend.person? && person.person?
-      email = friend ? friend.user.email : friend_email
-      if person && email && person.user.email == email
-        self.errors.add(:base, _("You can't invite youself"))
-      end
+    email = friend && friend.person? ? friend.user.email : friend_email
+    if person && email && person.user.email == email
+      self.errors.add(:base, _("You can't invite youself"))
     end
   end
 
@@ -141,18 +138,10 @@ class Invitation < Task
   end
 
   def environment
-    self.requestor.environment
-  end
-
-  def requestor_is_person
-    unless requestor.person?
-      errors.add(:invitation, N_('Requestor must be a person.'))
-    end
-  end
-
-  def target_is_person
-    unless target.person?
-      errors.add(:invitation, N_('Target must be a person.'))
+    if self.requestor
+      self.requestor.environment
+    else
+      nil
     end
   end
 
diff --git a/app/models/moderate_user_registration.rb b/app/models/moderate_user_registration.rb
index 0f0cb37..a8a1bf9 100644
--- a/app/models/moderate_user_registration.rb
+++ b/app/models/moderate_user_registration.rb
@@ -7,7 +7,7 @@ class ModerateUserRegistration < Task
 
   after_create :schedule_spam_checking
 
-  validate :target_is_environment
+  validates :target, kind_of: {kind: Environment}
 
   alias :environment :target
   alias :environment= :target=
@@ -58,10 +58,4 @@ class ModerateUserRegistration < Task
     _("User \"%{user}\" just requested to register. You have to approve or reject it through the \"Pending Validations\" section in your control panel.\n") % { :user => self.name }
   end
 
-  def target_is_environment
-    unless environment.class == Environment
-      errors.add(:moderate_user_registration, N_('Target must be an environment.'))
-    end
-  end
-
 end
\ No newline at end of file
diff --git a/app/models/suggest_article.rb b/app/models/suggest_article.rb
index 768f461..38d7df1 100644
--- a/app/models/suggest_article.rb
+++ b/app/models/suggest_article.rb
@@ -4,8 +4,6 @@ class SuggestArticle < Task
   validates_presence_of :email, :name, :if => Proc.new { |task| task.requestor.blank? }
   validates_associated :article_object
 
-  validate :target_is_organization
-
   settings_items :email, :type => String
   settings_items :name, :type => String
   settings_items :ip_address, :type => String
@@ -95,9 +93,4 @@ class SuggestArticle < Task
     self.delay.marked_as_ham
   end
 
-  def target_is_organization
-    unless target.organization?
-      errors.add(:suggest_article, N_('Target must be an organization.'))
-    end
-  end
 end
diff --git a/app/models/task.rb b/app/models/task.rb
index fe5ee04..a70dbb6 100644
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -116,6 +116,51 @@ class Task < ActiveRecord::Base
     end
   end
 
+  class KindOfValidator < ActiveModel::EachValidator
+    def validate_each(record, attribute, value)
+      environment = record.environment || Environment.default
+      klass = options[:kind]
+      group = klass.to_s.downcase.pluralize
+      id = attribute.to_s + "_id"
+      if environment.respond_to?(group)
+        attrb = value || environment.send(group).find_by_id(record.send(id))
+      else
+        attrb = value || klass.find_by_id(record.send(id))
+      end
+      if attrb.respond_to?(klass.to_s.downcase + "?")
+        unless attrb.send(klass.to_s.downcase + "?")
+          record.errors[attribute] << (options[:message] || "should be "+ klass.to_s.downcase)
+        end
+      else
+        unless attrb.class == klass
+          record.errors[attribute] << (options[:message] || "should be "+ klass.to_s.downcase)
+        end
+      end
+    end
+  end
+
+  def requestor_is_of_kind(klass, message = nil)
+    error_message = message ||= _('Task requestor must be '+klass.to_s.downcase)
+    group = klass.to_s.downcase.pluralize
+    if environment.respond_to?(group) and requestor_id
+      requestor = requestor ||= environment.send(klass.to_s.downcase.pluralize).find_by_id(requestor_id)
+    end
+    unless requestor.class == klass
+      errors.add(error_message)
+    end
+  end
+
+  def target_is_of_kind(klass, message = nil)
+    error_message = message ||= _('Task target must be '+klass.to_s.downcase)
+    group = klass.to_s.downcase.pluralize
+    if environment.respond_to?(group) and target_id
+      target = target ||= environment.send(klass.to_s.downcase.pluralize).find_by_id(target_id)
+    end
+    unless target.class == klass
+      errors.add(error_message)
+    end
+  end
+
   def close(status, closed_by)
     self.status = status
     self.end_date = Time.now
diff --git a/lib/noosfero/api/helpers.rb b/lib/noosfero/api/helpers.rb
index 54de70e..3a6afac 100644
--- a/lib/noosfero/api/helpers.rb
+++ b/lib/noosfero/api/helpers.rb
@@ -48,7 +48,6 @@ module Noosfero
       Rails.application.eager_load!
       ARTICLE_TYPES = ['Article'] + Article.descendants.map{|a| a.to_s}
       TASK_TYPES = ['Task'] + Task.descendants.map{|a| a.to_s}
-      
 
       def find_article(articles, id)
         article = articles.find(id)
diff --git a/test/functional/tasks_controller_test.rb b/test/functional/tasks_controller_test.rb
index 49d0d6d..b2aee1f 100644
--- a/test/functional/tasks_controller_test.rb
+++ b/test/functional/tasks_controller_test.rb
@@ -114,11 +114,23 @@ class TasksControllerTest < ActionController::TestCase
   end
 
   should 'affiliate roles to user after finish add member task' do
-    t = AddMember.create!(:person => profile, :organization => profile)
-    count = profile.members.size
+    c = fast_create(Community)
+    p = create_user('member').person
+
+    @controller.stubs(:profile).returns(c)
+    c.affiliate(profile, Profile::Roles.all_roles(profile.environment.id))
+
+    t = AddMember.create!(:person => p, :organization => c)
+
+    count = c.members.size
+
     post :close, :tasks => {t.id => {:decision => 'finish', :task => {}}}
-    profile = Profile.find(@profile.id)
-    assert_equal count + 1, profile.members.size
+    t.reload
+    
+    ok('task should be finished') { t.status == Task::Status::FINISHED }
+
+    c.reload
+    assert_equal count + 1, c.members.size
   end
 
   should 'display a create ticket form' do
diff --git a/test/unit/api/task_test.rb b/test/unit/api/task_test.rb
index ec478ed..81ccb09 100644
--- a/test/unit/api/task_test.rb
+++ b/test/unit/api/task_test.rb
@@ -68,12 +68,6 @@ class TasksTest < ActiveSupport::TestCase
     assert_not_nil json["task"]["id"]
   end
 
-  should 'not create task in a community' do
-    community = fast_create(Community)
-    post "/api/v1/communities/#{community.id}/tasks?#{params.to_query}&content_type=ApproveArticle"
-    assert_equal 400, last_response.status
-  end
-
   should 'create task defining the requestor as current profile logged in' do
     community = fast_create(Community)
     community.add_member(person)
@@ -167,12 +161,6 @@ class TasksTest < ActiveSupport::TestCase
     assert_not_nil json["task"]["id"]
   end
 
-  should 'not create task in a enterprise' do
-    enterprise = fast_create(Enterprise)
-    post "/api/v1/enterprises/#{enterprise.id}/tasks?#{params.to_query}&content_type=ApproveArticle"
-    assert_equal 400, last_response.status
-  end
-
   should 'create task defining the target as the enterprise' do
     enterprise = fast_create(Enterprise)
     enterprise.add_member(person)
diff --git a/test/unit/approve_article_test.rb b/test/unit/approve_article_test.rb
index b7a93d8..d7a32ec 100644
--- a/test/unit/approve_article_test.rb
+++ b/test/unit/approve_article_test.rb
@@ -427,7 +427,7 @@ class ApproveArticleTest < ActiveSupport::TestCase
     article = fast_create(Article)
     profile.domains << create(Domain, :name => 'example.org')
     assert_nothing_raised do
-      create(ApproveArticle, :article => article, :target => profile, :requestor => community)
+      create(ApproveArticle, :article => article, :target => profile, :requestor => profile)
     end
   end
 
--
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