```ruby
# For sharing functionality between FacebookContent and TwitterContent
require 'active_support/concern'

module ContentBase
  extend ActiveSupport::Concern

  included do
    belongs_to :link
    belongs_to :user

    has_many :posts, as: :content

    validates :body, presence: true

    attr_accessible :body
  end
end
```

Make link_id mass-assignable on contents
user
```ruby
# For sharing functionality between FacebookContent and TwitterContent
require 'active_support/concern'

module ContentBase
  extend ActiveSupport::Concern

  included do
    belongs_to :link
    belongs_to :user

    has_many :posts, as: :content

    validates :body, presence: true

    attr_accessible :body, :link_id
  end
end
```
assistant