[RUBY] Rails [For beginners] Implementation of comment function

I summarized the implementation of the comment function in rails.

Premise

The development environment for Ruby on Rails is in place. Posts (post table) and User (user table) have already been created. The User table uses gem devise. This time we will implement a comment for the post.

Implementation of comment function

1. Creating a Comment model

The details and relations of the Comments table to be created are as follows.

Modeling in the terminal

$ rails g model comment

Description of migration file

20********_create_comments.rb

class CreateComments < ActiveRecord::Migration[6.0]
  def change
    create_table :comments do |t |
      #Described from here
      t.references :user,foreign_key: true
      t.references :post, foreign_key: true
      t.text :text,nul: false
      #Described so far
      t.timestamps
    end
  end
end

Migration file adaptation

$ rails db:migrate

Link the Comment model, User model, and Post model

app/models/comment.rb

class Comment < ApplicationRecord
  belongs_to :user
  belongs_to :post
end

app/models/user.rb

class User < ApplicationRecord
  has_many :posts
  has_many :comments
end

app/models/post.rb

class Comment < ApplicationRecord
  has_many :users
  has_many :comments
end

2. Creating a routing

routes.rb

Rails.application.routes.draw do
  resources :users
  resources :posts do
    resource :comments
  end
end

3. Creating a Comments controller

comments_controller.rb

class CommentsController < ApplicationController
  def create
    @comment = Comment.create(comment_params)
    redirect_back(fallback_location: root_path)
  end

 private

  def comment_params
    params.require(:comment).permit(:text).merge(user_id: current_user.id, post_id: params[:post_id])
  end
end

posts_controller.rb

class PostsController < ApplicationController
  def new
    @post = Post.new
  end

  def create
    @post = Post.new(post_params)
    if @post.save
      redirect_to user_url(current_user)
    else
      render :new
    end
  end
  
  def show
    #Write comment instance creation
    #This time Posts#I would like to implement a comment function in show.
    @comment = Comment.new
    @comments = @post.comment_cs.includes(:user)
  end

private

  def post_params
    params.require(:post).permit(:text).merge(user_id: current_user.id)
  end

  def set_post
    @post = Post.find(params[:id])
  end
 
end

4. Create a view

Write a description of the comment function on the post details page.

erb:views/posts/show.html.erb

#abridgement

 <%= form_with model: [@post,@comment],merhod: :post,locals: true do | form | %>
    <%= form.text_area :text %>
    <%= form.submit "Post" %>
 <% end %>

#abridgement

Comment function completed!

Summary

This time, I started the comment function in Rails from table creation. I am also a beginner in programming, so please let me know if you make any mistakes. Thank you for reading until the end!