Having multiple instance variables in rails controller action? (Rails best practices)

Question

Say for example I have two models, posts and category. Now say I want to make it so the from the category show page you can create a new post using the form_for method. To do this, you will obviously need access to the @category variable and a new instance of a post (@post). Is this acceptable code in the controller?

#app/controllers/categories_controller.rb
def show
  @category = Category.find(params[:id])
  @post = Post.new
end

Or is it bad practice to have two instance variables defined in the one controller action - and if it is, what would be the best practice for a case like this?

How are Post and Category related? Could you show that as well? — vee
– vee, Commented Apr 2, 2015 at 3:14

Brad Werth · Accepted Answer · 2015-04-02 05:10:22Z

2

I usually do something like:

#app/controllers/categories_controller.rb

helper_method :category
helper_method :post

def show
end

private

def category
  @_category ||= params[:id] ? Category.find(params[:id]) : Category.new(params[:category])
end

def post
  @_post ||= Post.new(params[:post])
end

Then, in your views, just refer to post or category (not @post or @_post). The nice thing is you can remove the same logic from your new, delete, etc methods...

answered Apr 2, 2015 at 5:10

Brad Werth

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Rahul · Accepted Answer · 2015-04-02 03:11:03Z

0

Actions related to posts should be in the PostsController as much as possible.

Let's say the user is looking at all posts under the category "rails": /categories/rails

There's a button on that page to create a new post under the "rails" category, href: /posts/new?category=rails

This takes you to PostsController#new where you instantiate a new Post, validate the category param and build a view. This view could either be a new page, or a modal popping up.

answered Apr 2, 2015 at 3:11

Rahul

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2 Comments

Jake Over a year ago

I don't necessarily agree with this. Although it might be a "best practice" there are definitely times where you might want to do it like OP is doing, such as replying to a forum thread via a quick reply box. It depends on the situation.

Harazzy Over a year ago

@Jake0oo0 Yes I probably should have elaborated that I was doing a modal popup here and wanted to know if this still was the best way to go about it

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