Railsでhas_many throughな関係で、チェックボックスの値をupdateする方法

Question

###Article Model

class Article < ActiveRecord::Base
  has_many :articles_categories
  has_many :categories, through: :articles_categories
end

###Category Model

class Category < ActiveRecord::Base
  has_many :articles_categories
  has_many :articles, through: :articles_categories
end

###ArticlesCategory Model

class ArticlesCategory < ActiveRecord::Base
  belongs_to :article
  belongs_to :category
end

###ArticlesContoller

class ArticlesController < ApplicationController
  before_action :set_article, only: [:show, :edit, :update, :destroy]

  def edit
    #@genreにcategoryの一つであるgenre（国際、環境、貧困、障害など）をいれる
    @genre = Group.genre.first.categories
    @selected_categories = ArticlesCategory.where(article_id: params[:id])
    @selected_categories_id = []
    @selected_categories.each do |sci|
      @selected_categories_id << sci.category_id
    end
  end

  def update
    begin
    @article.update!(article_params)
    redirect_to edit_article_path(@article.id), notice: 'Article was successfully created.'
    rescue Exception => e
      render :edit
    end
 end

 private
    def set_article
      @article = Article.find(params[:id])
    end

    def article_params
      params.require(:article).permit(:title, :kind, :price_category, :place_category, :place, :price, :term_category, :activity_frequent_category, :necessary_time_category, :target, :deadline, :detail_info, :subtitle, :participation_comment, :atmosphere, :participation_number, :men_rate, :women_rate, :user_id, pictures_attributes: [:file, :description], remarkable_points_attributes: [:text], activity_dates_attributes: [:start_date, :end_date], additional_questions_attributes: [:name, :necessary])
    end
end

###articles/edit.html.erb

<%= form_for(@article) do |f| %>
  <div class="field">
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </div>

  <div class="field">
    <%= f.label :genre %><br>
    <% @genre.each do |genre| %>
      <% if @selected_categories_id.include?(genre.id) then %>
     <%= check_box "categories", "#{gemre.status}", {:checked => true} %>
    <% else %>
      <%= check_box "categories", "#{genre.status}" %>
    <% end %>
      <%= label_tag "#{genre.name}" %>
    <% end %>
  </div>

  <%= f.submit %>

<% end %>

当然ではあるのですが、
このままではarticle_paramsの内容しかupdateされず、
いろいろ試しましたがCategoryの中身をupdateする方法が見つかっていません。

createでは、

  def create
    @article = Article.new(article_params)
    @article.user_id = current_user.id
    params[:categories].each do |key, value|
      @article.categories << Category.find(key.to_i) if value == "1"
    end
    begin
      @article.save!
       redirect_to edit_article_path(@article.id), notice: 'Article was successfully created.'
    rescue Exception => e
      render :new
    end
  end

こんな感じで保存してます。

ご教授よろしくお願いします。