Ruby on rails Rails—创建新模型所需的帮助

我想创建模型

消息

，以便

人员

可以在

组#show

页面中发布新消息。但为此，她/他必须来自相关的

组

，或所有者，或拥有该组的组成员（成为成员）

模型

消息的关联如何？
类消息class Person
  has_many :owned_groups, :class_name => "Group", :foreign_key => :owner_id
  has_many :owned_group_memberships, :through => :owned_groups, 
              :source => :group_memberships 

  has_many :group_memberships, :foreign_key => "member_id"
  has_many :groups, :through => :group_memberships

end

class GroupMembership
  belongs_to :member, :class_name => 'Person'
  belongs_to :group
end

class Group
  belongs_to :owner, :class_name => "Person"
  has_many :group_memberships
  has_many :members, :through => :group_memberships
end

属于某人
属于：组
验证：具有组权限
def具有组权限
除非self.person.owned_groups.include？（self.group）| self.person.groups.include？（self.group）
self.errors.add（：base，“您没有向该组添加邮件的权限。”
结束
结束
结束

class Message < ActiveRecord::Base
  belongs_to :person
  belongs_to :group
  validate :has_group_permission

  def has_group_permission
    unless self.person.owned_groups.include?(self.group) || self.person.groups.include?(self.group)
      self.errors.add(:base, "you don't have permission to add a message to this group."
    end
  end
end