Add comments'

app/controllers/comments_controller.rb

@@ -0,0 +1,13 @@
+class CommentsController < ApplicationController
+  before_action :set_article
+
+  def create
+    @article.comments.create! params.required(:comment).permit(:content)
+    redirect_to @article
+  end
+
+  private
+    def set_article
+      @article = Article.find(params[:article_id])
+    end
+end