"Cannot redirect to nil!" - ruby-on-rails

Question

I'm following along with Michael Hartl's rails tutorial and making small adjustments. Users can make microposts (status updates) on their profiles, at which point the page will appear to reload and their new status will be displayed. I can confirm by hand that this works exactly as intended. The problem is that tests for it aren't passing for some reason, even though the end result outside of tests looks perfect.
Screenshots of microposts_controller.rb, microposts_interface_test.rb (the failing test), related error messages, and users_controller.rb, in that order: http://imgur.com/a/IS1HI
microposts_controller.rb
class MicropostsController < ApplicationController
before_action :logged_in_user, only: [:create, :destroy]
before_action :correct_user, only: :destroy
def create
#micropost = current_user.microposts.build(micropost_params)
if #micropost.save
flash[:success] = "Status updated!"
redirect_to #user
else
#feed_items = []
flash[:warning] = "Status was blank!"
redirect_to #user
end
end
def destroy
#micropost.destroy
flash[:success] = "Status deleted."
redirect_to #user
end
microposts_interface_test.rb:
require 'test_helper'
class MicropostsInterfaceTest < ActionDispatch::IntegrationTest
def setup
#user = users(:mrtestit)
end
test "micropost interface" do
log_in_as(#user)
assert is_logged_in?
# Invalid submission
assert_no_difference 'Micropost.count' do
post microposts_path, micropost: { content: "" }
end
# Valid submission
content = "This status really ties the room together"
assert_difference 'Micropost.count', 1 do
post microposts_path, micropost: { content: content }
end
follow_redirect!
assert_match content, response.body
# Delete a post.
assert_select 'a', text: 'delete'
first_micropost = #user.microposts.paginate(page: 1).first
assert_difference 'Micropost.count', -1 do
delete micropost_path(first_micropost)
end
# Visit a different user.
get user_path(users(:archer))
assert_select 'a', text: 'delete', count: 0
end
end
users_controller.rb:
class UsersController < ApplicationController
before_action :logged_in_user, only: [:index, :edit, :update, :destroy]
before_action :correct_user, only: [:edit, :update]
before_action :admin_user, only: :destroy
def index
#users = User.where(activated: true).paginate(page: params[:page])
end
def show
#user = User.find(params[:id])
if logged_in?
#micropost = current_user.microposts.build
#feed_items = current_user.feed.paginate(page: params[:page])
end
#microposts = #user.microposts.paginate(page: params[:page])
redirect_to root_url and return unless #user.activated?
end
I understand that, for some reason, this is saying that #user is nil. However, I've confirmed many times over that redirect_to #user works everywhere else.
The fact that every other test passes is already proof of that, but just to go the extra mile, I've confirmed that the failing redirect_to #user line of code works in other files, such as when a user updates their profile information under their settings page and is then redirected to their profile page. I've spent over 10 hours working on this (mostly yesterday) and am on the verge of simply deleting this test and moving on with my life. Stackoverflow is my last resort.

Answer 1

I think that you must change
redirect_to #user
to
redirect_to current_user
#user is class instance variable and must be created manually, eg:
#user = User.find_by_id post.owner_id
While current_user is global variable and can be used anywhere.
But don't forget check it to nil because of user can be not signed in!
You can check it manually by unless current_user.nil? in each method or better add helper method and use it in your controllers, tutorial already describes this way:
module SessionHelper
def signed_in_user
unless signed_in?
store_location
redirect_to signin_url, notice: "Please sign in."
end
end
# ...
class MicropostsController < ApplicationController
before_action :signed_in_user
# ...
Update:
For Aleks's advice: if you want redirect to post's owner that might be not current user, use
user = micropost.owner
redirect_to user

Answer 2

There are two possible solutions for this.
First one is this:
Change this:
def create
#micropost = current_user.microposts.build(micropost_params)
if #micropost.save
flash[:success] = "Status updated!"
redirect_to #user
else
#feed_items = []
flash[:warning] = "Status was blank!"
redirect_to #user
end
end
to this:
def create
#micropost = current_user.microposts.build(micropost_params)
if #micropost.save
flash[:success] = "Status updated!"
redirect_to current_user
else
#feed_items = []
flash[:warning] = "Status was blank!"
redirect_to current_user
end
end
OR (if first doesn't work) the second approach:
Update this line:
before_action :correct_user, only: :destroy
to:
before_action :correct_user, only: [:create, :destroy]