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Model association

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Creating comments for articles.

shell
rails generate model Comment commenter:string body:text article:references
rails db:migrate
rails generate controller Comments

Tell rails that articles has many comments ​

ruby
## app/models/article.rb
class Article < ApplicationRecord
  has_many :comments
  validates :title, presence: true, length: { minimum: 5 }
end

## config/routes.rb
resources :articles do
  resources :comments
end

Adding and viewing comments ​

ruby
## app/controllers/comments_controller.rb
class CommentsController < ApplicationController
  def create
    @article = Article.find(params[:article_id])
    @comment = @article.comments.create(comment_params)
    redirect_to article_path(@article)
  end

  private
  def comment_params
    params.require(:comment).permit(:commenter, :body)
  end
end
erb
<!-- app/views/articles/show.html.erb -->
<p>
  <strong>Title:</strong>
  <%= @article.title %>
</p>

<p>
  <strong>Text:</strong>
  <%= @article.text %>
</p>

<h2>Comments</h2>
<% @article.comments.each do |comment| %>
  <p>
    <strong>Commenter:</strong>
    <%= comment.commenter %>
  </p>

  <p>
    <strong>Comment:</strong>
    <%= comment.body %>
  </p>
<% end %>

<h2>Add a comment:</h2>
<%= form_with(model: [ @article, @article.comments.build ], local: true) do |form| %>
  <p>
    <%= form.label :commenter %><br>
    <%= form.text_field :commenter %>
  </p>
  <p>
    <%= form.label :body %><br>
    <%= form.text_area :body %>
  </p>
  <p>
    <%= form.submit %>
  </p>
<% end %>

<%= link_to 'Edit', edit_article_path(@article) %> |
<%= link_to 'Back', articles_path %>