sujection重构

  def create
    @subjection = @subject.subjections.new
    if params[:video_or_show_id].length == 20
      show = Show.where(:showid => params[:video_or_show_id]).try(:first)
      if show.present?
        @show = show
      else
        begin
          @show = Show.build_from_show_id(params[:video_or_show_id])
          @subjection.subjectable_type = "show"
          @subjection.subjectable_id = @show.id
          @subjection.title = @show.showname
          @subjection.sub_title = @show.showsubtitle
          @subjection.description = @show.showdesc
          @subjection.save
          if @show.save
            img_v = @subjection.pictures.new(:url => @show.show_vthumburl,
                                             :name => "img_v")
            img_v.save
            img_h = @subjection.pictures.new(:url => @show.show_thumburl,
                                             :name => "img_h")
            img_h.save
          end
        rescue ArgumentError, Youku::DS::Error => e
          @show = Show.new
          @show.errors.add(:base, e.message)
          redirect_to new_subject_subjection_path(@subject), :notice => "视频没有版权"
        end
      end
    else
      video = Video.where(:videoid => params[:video_or_show_id]).try(:first)
      if video.present?
        @video = video
      else
        begin
          @video = Video.build_from_video_id(params[:video_or_show_id])
          if @video.videoid.present?
            @subjection.subjectable_type = "video"
            @subjection.subjectable_id = @video.id
            @subjection.description = @video.desc
            @subjection.title = @video.title
            @subjection.save
            if @video.save
              img_h = @subjection.pictures.new(:url => @video.thumburl,
                                               :name => "img_h")
              img_h.save
            end
          end
        rescue ArgumentError, Youku::DS::Error => e
          @video = Video.new
          @subjection.errors.add(:base, e.message)
          render :error and return
        end
      end
    end

    if @subjection.save
      redirect_to subject_subjections_url(@subject), notice: '新建成功'
    else
      render :new
    end
  end

修改后

if persisted? # 如果是已经保存到数据库的 ActiveRecord 对象
  super # 则调用原始的 subjectable= 方法

只有在新建一个 subjection 时，调用 subjectable= 方法的时做一些特殊处理，
比如给 title, sub_title 和 description 赋值

def create
  @subjection = @subject.subjections.build
  id = params[:video_or_show_id]

  subjectable = if id.length == 20
                  find_or_create_show_from_show_id(id)
                else
                  find_or_create_video_from_video_id(id)
                end

  @subjection.subjectable = subjectable

  if @subjection.save
    redirect_to subject_subjections_url(@subject), notice: '新建成功'
  else
    render :error
  end
rescue ArgumentError, Youku::DS::Error => e
  @subjection.errors.add(:base, e.message)
  render :error
end

private
  def find_or_create_show_from_show_id(id)
    if show = Show.find_by_showid(id)
      show
    else
      show = Show.build_from_show_id(id)
      show.save
      show
    end
  end

  def find_or_create_video_from_video_id(id)
    if video = Video.find_by_videoid(id)
      video
    else
      video = Video.build_from_video_id(id)
      video.save
      video
    end
  end

def subjectable=(subjectable)
  if persisted?
    super
  else
    self.attributes = {
      subjectable_type: subjectable.class.name,
      subjectable_id: subjectable.id
    }

    case subjectable
    when Show
      self.attributes = {
        title: subjectable.showname,
        sub_title: subjectable.showsubtitle,
        description: subjectable.showdesc,
        pictures_attributes: [{ name: 'img_h', url: subjectable.show_thumburl },
                              { name: 'img_v', url: subjectable.show_vthumburl }]
      }
    when Video
      self.attributes = {
        title: subjectable.title,
        description: subjectable.desc,
        pictures_attributes: [{ name: 'img_h', url: subjectable.thumburl }]
      }
    else
      super  
    end
  end
end