Полето за множествен избор Simple_form не работи

нов потребител на релси тук. Опитвам се да накарам моя формуляр за график да съхранява масив от „дни“, но след няколко опита просто не мога да го накарам да работи.

Ето моите кодове в момента

*schedules/_form.html.erb:*

    <%= simple_form_for @schedule do |f| %>
  <% if @schedule.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@schedule.errors.count, "error") %> prohibited this schedule from being saved:</h2>

      <ul>
      <% @schedule.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <%= f.input :section_id do %>
<%= f.select :section_id, Section.all.map{|s| [s.seccon, s.id]}, :include_blank => true %>
<% end %>

<%= f.association :subject %>


<%= f.collection_select :day_ids, @days, :id, :name, {}, {:multiple => true, :size => 1} %>


   <div class="field">
   <%= f.label :start_time %>
     <%= f.time_select :start_time %>
   </div>
<%= f.input :professor do %> 
        <%= f.select :professor_id, Professor.all.map{|j| [j.procon, j.id]}, :include_blank => true %>
    <% end %>


    <%= f.association :room %>


      <%= f.button :submit %>

 <% end %>

*schedules_controller.rb:*

class SchedulesController < ApplicationController
  before_action :set_schedule, only: [:show, :edit, :update, :destroy]

  # GET /schedules
  # GET /schedules.json
  def index
    @schedules = Schedule.all
    @days = Day.all
  end

  # GET /schedules/1
  # GET /schedules/1.json
  def show
  end

  # GET /schedules/new
  def new
    @schedule = Schedule.new
    @days = Day.all
  end

  # GET /schedules/1/edit
  def edit
  end

  # POST /schedules
  # POST /schedules.json
  def create
    @schedule = Schedule.new(schedule_params)
    @days = Day.all

    respond_to do |format|
      if @schedule.save
        format.html { redirect_to @schedule, notice: 'Schedule was successfully created.' }
        format.json { render action: 'show', status: :created, location: @schedule }
      else
        format.html { render action: 'new' }
        format.json { render json: @schedule.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /schedules/1
  # PATCH/PUT /schedules/1.json
  def update


    respond_to do |format|
      if @schedule.update(schedule_params)
        format.html { redirect_to @schedule, notice: 'Schedule was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @schedule.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /schedules/1
  # DELETE /schedules/1.json
  def destroy
    @schedule.destroy
    respond_to do |format|
      format.html { redirect_to schedules_url }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_schedule
      @schedule = Schedule.find(params[:id])
      @days = Day.all
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def schedule_params
      params.require(:schedule).permit(:section_id, :subject_id, :start_time, :finish_time_id, :professor_id, :room_id, :day_ids)
    end
end

schedule.rb:

class Schedule < ActiveRecord::Base
  belongs_to :section
  belongs_to :subject
  belongs_to :finish_time
  has_and_belongs_to_many :days
  accepts_nested_attributes_for :days, :allow_destroy => true

  validates :section_id, :subject_id, :start_time, :professor_id, :room_id, :presence => true

  belongs_to :professor
  belongs_to :room
end

day.rb:

class Day < ActiveRecord::Base

has_and_belongs_to_many :schedules
default_scope { order(:id)}

has_paper_trail

validates :name, :desc, :presence => true

end