ruby - Rails 4 ArgumentError in Controller#create -

i'm trying create web application allows users add videos youtube getting argumenterror in videoscontroller#create:

the provided regular expression using multiline anchors (^ or $), may present security risk. did mean use \a , \z, or forgot add :multiline => true option?

videocontroller.rb

class videoscontroller < applicationcontroller       def index     @videos = video.order('created_at desc')   end     def new     @video = video.new   end    def create     @video = video.new(video_params)     if @video.save         flash[:success] = 'video added!'         redirect_to root_url     else         render 'new'     end   end    def video_params     params.require(:video).permit(:link)   end end 

videos.rb

class video < activerecord::base   yt_link_format = /^.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/i   before_create ->     uid = link.match(yt_link_format)      self.uid = uid[2] if uid && uid[2]      if self.uid.to_s.length != 11       self.errors.add(:link, 'is invalid.')       false     elsif video.where(uid: self.uid).any?       self.errors.add(:link, 'is not unique.')       false     else       get_additional_info     end   end      validates :link, presence: true, format: yt_link_format    private 

do add \a , \z yt_link_format line?

in videos.rb change definition of yt_link_format:

yt_link_format = /\a.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*\z/i 

(basically replacing initial ^ \a, , putting \z @ end)

\a , \z match beginning , end of string; ^ , $ match beginning , end of line. since not defining regex multiline need use string matchers not line ones.

it's error trying tell you; it's bit better described in api documentation here: http://apidock.com/rails/activemodel/validations/helpermethods/validates_format_of