Rails 4 nested attributes multiple records when updating

I'm stuck and i don't know why it is not working right. I have a model lesson wich has many sublessons. When i update the lesson rails update properly the lesson attributes but is creating another sublessons records instead of just updating it.

Here is my code

View Form: <div style="padding:13px"> <%= form_for @lesson do |f| %>           <%= f.label :lesson_name, "Lesson title" %></br>           <%= f.text_field :lesson_name, class: "form-control" %></br>           <%= f.label :lesson_icon, "Choise icon" %>           <%= f.select "lesson_icon", options_for_select([ "ico03", "ico04","ico05","ico06" ])%></br></br>           <div>            <%= f.fields_for :sublessons do |sublesson_a| %>

           <%= sublesson_a.label :sublesson_name, "Subtitle 1" %></br>            <%= sublesson_a.text_field :sublesson_name, class: "form-control" %></br>            <%= sublesson_a.label :sublesson_content, "Content" %></br>            <%=sublesson_a.text_area 'sublesson_content', rows: 3, class: 'form-control'%></br>            <%= sublesson_a.label :sublesson_video_link, "Video link" %><br>            <%= sublesson_a.text_field :sublesson_video_link, class: "form-control" %></br>           <%end%>          </div>        </div> <%= f.submit "Submit", class: "btn btn-primary" %>

<% end %>


lesson model class Lesson < ActiveRecord::Base    has_many :sublessons, :dependent => :destroy    accepts_nested_attributes_for :sublessons, :reject_if => :all_blank end sublesson model

class Sublesson < ActiveRecord::Base   belongs_to :lesson, :foreign_key => "lesson_id"   validates :sublesson_name, presence: true   validates :sublesson_content ,presence: true end

lesson controller

def update    @lesson = Lesson.find(params[:id])    @sublessons=@lesson.sublessons.all     if @lesson.update(lesson_params)       flash[:notice] = "Lesson updated"       redirect_to lessons_show_url     else       flash[:notice] = "Error"       redirect_to lessons_show_url     end end

def edit     @lesson = Lesson.find(params[:id])     @sublessons=@lesson.sublessons.all end

def lesson_params params.require(:lesson).permit(:lesson_name, :lesson_icon, sublessons_attributes:[:sublesson_id, :sublesson_name, :sublesson_content, :sublesson_video_link])   end