How implement the Has Many Through Association on Controllers and methods - ruby-on-rails

Question

in my app I'm creating the categories in admin(so the admins creates, updates and destroys the categories name) and then when the users will create the posts they will select( or I'm thinking for switch with checkbox) a category for the posts.
I decide to do this implementation with a has many through for posts and categories. But I' having doubts for implements:
the post_params;
the methods for add the categories and then destroy the categories
and the parts for create, update and destroy the posts.
How can I implement this? It's a better way do different? So if someone help me with this I will appreciate.
Post.rb
class Post < ActiveRecord::Base
has_many :categorizations
has_many :categories, through: :categorizations
...
def add_category(category)
categorizations.create(category_id: category.id)
end
def remove_category(category)
categorizations.find_by(category_id: category.id).destroy
end
category.rb
class Category < ActiveRecord::Base
has_many :categorizations
has_many :posts, through: :categorizations
validates :name,
presence: true,
length: { minimum: 3, maximum: 30 },
uniqueness: true
end
categorization.rb
class Categorization < ActiveRecord::Base
belongs_to :post
belongs_to :category
validates :post_id, presence: true
validates :category_id, presence: true
end
controllers/admin/PostsController
class Admin::PostsController < Admin::ApplicationController
def new
#post = Post.new
#categories = Category.all.map{ |c| [c.name, c.id]}
end
def create
#post = Post.new(post_params)
#post.author = current_user
#post.categories << params[:category_id]
if #post.save
flash[:notice] = "Post has been created."
redirect_to #post
else
flash[:alert] = "Post has not been created."
render "new"
end
end
def destroy
#post = Post.find(params[:id])
#post.destroy
flash[:notice] = "Post has been deleted."
redirect_to posts_path
end
private
def post_params
params.require(:post).permit(:title,
:subtitle,
:content,
:attachment,
:attachment_cache,
:remote_attachment_url,
:categorizations_attributes => [:id,
:post_id,
:category_id,
:_destroy,
:categories_attributes => [:id,
:name]
]
)
end
end
controllers/posts_controller.rb
class PostsController < ApplicationController
before_action :set_post, only: [:show, :edit, :update]
def index
#posts = policy_scope(Post)
end
def show
authorize #post, :show?
end
def edit
authorize #post, :update?
end
def update
authorize #post, :update?
if #post.update(post_params)
flash[:notice] = "Post has been updated."
redirect_to #post
else
flash.now[:alert] = "Post has not been updated."
render "edit"
end
end
private
def set_post
#post = Post.find(params[:id])
rescue ActiveRecord::RecordNotFound
flash[:alert] = "The post you were looking for could not be found."
redirect_to posts_path
end
def set_category
#category = Category.find(params[:category_id])
end
def post_params
params.require(:post).permit(:title, :subtitle, :content, :attachment, :attachment_cache, :remove_attachment, :remote_attachment_url, :category_id)
end
end
posts/_form.html.slim
= simple_form_for([:admin, #post], :html => { :multipart => true }) do |f|
= select_tag(:category_id, options_for_select(#categories), :prompt => "Select ad Category")
routes
Rails.application.routes.draw do
namespace :admin do
root 'application#index'
resources :posts, only: [:new, :create, :destroy]
resources :categories
resources :users do
member do
patch :archive
end
end
end
devise_for :users
root "posts#index"
resources :posts, only: [:index, :show, :edit, :update]
end

Answer 1

In your form
= select_tag(:category_ids, options_for_select(#categories), :prompt => "Select ad Category", multiple: true)
In your controller
params.require(:post).permit(:title, :subtitle, :content, :attachment, :attachment_cache, :remove_attachment, :remote_attachment_url, :category_ids)
Also need to give some advise, in your posts_controller.rb
remove below line
rescue ActiveRecord::RecordNotFound
Insterad of this write it in application_controller.rb , so it will work for whole application.

Answer 2

What I do for fix was put on the PostsController this:
class Admin::PostsController < Admin::ApplicationController
before_action :set_categories, only: [:new, :create]
.
.
.
private
def set_categories
#categories = Category.all.select(:id, :name)
end
def post_params
params.require(:post).permit(:title,
:subtitle,
:content,
:attachment,
:attachment_cache,
:remote_attachment_url,
category_ids:[]
)
end
And on the form I changed for use checkboxes and with that I can select and add more categories for a Post:
= f.association :categories, label: "Select the Categories", as: :check_boxes , collection: #categories.map{|c| [c.name, c.id]}, include_hidden: false
Add on the class Post and Category a dependent: :destroy for destroy the joins properly.
has_many :categorizations, dependent: :destroy
has_many :categories, through: :categorizations
And was necessary delete the validation for post_id on categorization so I just comment because when was uncommented when I try to create a Post it wasn't possible, So I do this:
class Categorization < ActiveRecord::Base
belongs_to :post
belongs_to :category
#validates :post_id, presence: true
validates :category_id, presence: true
end
And work's!