保存之前的Rails访问模型属性

Question

I have notices and comments on those notices. The comments are also of class notice. When a notice is submitted for creation, its commentee_id will be blank if it is an original notice. If the notice is a comment on another notice, its commentee_id will be the id of the notice it is commenting on.

notices_controller.rb:

def create
  @character = Character.find_by(callsign: params[:callsign])
  @notice = @character.notices.build(notice_params)
  if @notice.save
    .
    .
  end
end

def notice_params
  params.require(:notice).permit( :content, :picture, :latitude, :longitude,
                                  active_comment_relationship_attributes: [:commentee_id] )
end

notice.rb:

belongs_to :character

has_one  :active_comment_relationship, class_name: "Commentrelationship",
                                       foreign_key: "commenter_id",
                                       dependent: :destroy
has_one  :supernotice, through: :active_comment_relationship, source: :commentee
accepts_nested_attributes_for :active_comment_relationship

before_validation  :create_commentee

private

  def create_commentee
    if !commentee_id.blank?
      create_active_comment_relationship(commentee_id: :commentee_id)
    end
  end

The new notice model doesn't get successfully created. I get the error message:

undefined local variable or method `commentee_id' for #<Notice:0x0000010c3a4708>)

When create_commentee is called, the new @notice instance has been created in memory but not yet saved to the database ( create_commentee is a before_validation callback). At this stage, how do you correctly access commentee_id ?

Neither this ( !commentee_id.blank? ):

def create_commentee
  if !commentee_id.blank?
    create_active_comment_relationship(commentee_id: :commentee_id)
  end
end

nor this ( commentee_id not :commentee_id ):

def create_commentee
  if !commentee_id.blank?
    create_active_comment_relationship(commentee_id: commentee_id)
  end
end

makes any difference.

Answer 1

At least one problem is that you're doing this:

if !:commentee_id.blank?

...when you should be doing this:

if !commentee_id.blank?

:commentee_id is a symbol, which is like a special kind of string, and it will never be blank (well, unless it's :"" ). You want to call the commentee_id method, ie without : ).

PS If you want to be slightly more idiomatic, I'd recommend this instead:

if commentee_id.present?