ruby on rails - Render new form if params are empty -

i have video upload form. works when video chosen computer , submitted. video gets uploaded. if user clicks on submit button without selecting video, throws following error:

actioncontroller::parametermissing in videoscontroller#create param missing or value empty: video 

what doing wrong here?

this video controller:

class videoscontroller < applicationcontroller     before_action :find_userinfo     before_action :find_video, only: [:destroy]     before_action :authenticate_user!, only: [:new]      def index     end      def new         @video = video.new     end      def create         @video = video.new(video_params)         @video.userinfo_id = @userinformation.id         @video.user_id = current_user.id           if @video.save             redirect_to userinfo_path(@userinformation)         else             render 'new'         end     end      def edit     end      def update     end      def destroy         @video.destroy         redirect_to userinfo_path(@userinformation)     end      private         def video_params             params.require(:video).permit(:introvideo)         end          def find_userinfo             @userinformation = userinfo.friendly.find(params[:userinfo_id])         end          def find_video             @video = video.find(params[:id])         end end 

my form view:

<%= simple_form_for([@userinformation, @userinformation.videos.build]) |f| %>     <%= f.file_field :introvideo%>     <%= f.button :submit, 'upload video'%> <% end %> 

i tried adding following code controller still didn't work:

def create     @video = video.new(video_params)     @video.userinfo_id = @userinformation.id     @video.user_id = current_user.id      if @video.video_params.empty?         render 'new'     end      if @video.save         redirect_to userinfo_path(@userinformation)     else         render 'new'     end end 

any appreciated. thanks.

to check if video empty this:

def create     return render 'new' if params[:video].blank?      @video = video.new(video_params)     @video.userinfo_id = @userinformation.id     @video.user_id = current_user.id      if @video.save         redirect_to userinfo_path(@userinformation)     else         render 'new'     end end