ArgumentError in Ruby on Rails track Project: Blog APP

Hi everyone ,

I am having ArgumentError
I am currently working on Ruby on Rails Track in **Project Blog App ** at Adding Comments section.

this is a Picture of the Error i get :

It says the form is expecting two arguments but i provided none !!!
I reviewed my codes line by line , but i do not know where my Mistake is ?!

Here are snippets of all the related Codes :

Codes from _form.html.erb :

<h4>Post a Comment </h4>
<%= form_for[@article, @comment] do |f| %>
<p>
<%= f.label :author_name %> <br>
<%= f.text_field :author_name %>
</p>
<p>
<%= f.label :body %> <br>
<%= f.text_area :body %>
</p>
<p>
<%= f.submit %> <br>
</p>
<%end%>

codes from articles_controller.rb

 def show
@article = Article.find(params[:id])
@comment = Comment.new
@comment.article_id = @article.id
end

codes from show.html.erb :

<h1><%= @article.title %></h1>
<p><%= @article.body%></p>
<h3>Comments </h3>
<%= render partial: 'comments/form' %>
<%= render partial: 'articles/comment', collection: @article.comments %>
<%= link_to "EDIT", edit_article_path(@article) %> <br>
<%= link_to "<< Back to Articles List", articles_path%> <br>
<%= link_to "Delete Article", article_path(@article), method: :delete%>

codes from routes.rb :

Rails.application.routes.draw do
root to: 'articles#index'
resources :articles do
resources :comments
end
end

codes from comments_controller.rb :

class CommentsController < ApplicationController
def create
@comment = Comment.new(comment_params)
@comment.article_id = params[:article_id]
@comment.save
 redirect_to article_path(@comment.article)
 end

def comment_params
params.require(:comment).permit(:author_name, :body)
end
end

I would really appreciate it i get any help or suggestion back !
Thanks,

It sounds crazy but the solution is
Adding a space between form_for and the []
The code for the form_for will be like :

<h4>Post a Comment </h4>
# one space was added between form_for and []
<%= form_for [@article, @comment] do |f| %>
<p>
<%= f.label :author_name %> <br>
<%= f.text_field :author_name %>
</p>
<p>
<%= f.label :body %> <br>
<%= f.text_area :body %>
</p>
<p>
<%= f.submit %> <br>
</p>
<%end%>