Pre-processing within a Rails Controller create method does not work - ruby-on-rails

Question

I am following Michael Hartl's tutorial, and trying to implement the reply twitter-like functionality, ie. "#122-john-smith: hello there" should be a reply to user 122.
I first tried filtering the "#XXX-AAA-AAA" part using a before_filter, but I decided to try it first in the very same Micropost#create action. So far I've got this MicropostController:
class MicropostsController < ApplicationController
before_filter :signed_in_user, only: [:create, :destroy]
before_filter :correct_user, only: [:destroy]
#before_filter :reply_to_user, only: [:create]
def index
end
def create
#micropost=current_user.microposts.build(params[:micropost])
#Rails.logger.info "hoooola"
regex=/\A#(\d)+(\w|\-|\.)+/i
message=#micropost.content.dup
isResponse=message.match(regex)[0].match(/\d+/)[0]
#micropost.response=isResponse
if #micropost.save
flash[:success]="Micropost created!"
redirect_to root_path
else
#feed_items=[]
render 'static_pages/home'
end
end
def destroy
#micropost.destroy
redirect_to root_path
end
private
def correct_user
#micropost = current_user.microposts.find_by_id(params[:id])
redirect_to root_path if #micropost.nil?
end
def reply_to_user
regex=/\A#(\d)+(\w|\-|\.)+/i
#I use [0] cause the output of match is a MatchData class with lots of bs
mtch=params[:micropost][:content].match(regex)[0]
#puts mtch
##micropost=current_user.microposts.build(params[:micropost])
if mtch != nil
user_id=mtch.match(/\d+/)[0]
#replied_user=User.find(user_id)
#micropost.response=user_id unless #replied_user.nil?
end
end
end
And this is the snippet test I'm trying to pass:
require 'spec_helper'
describe "MicropostPages" do
subject { page }
let(:user) { FactoryGirl.create(:user) }
before { valid_signin user }
describe "micropost creation" do
before { visit root_path }
describe "with invalid information" do
it "should not create a micropost" do
expect { click_button "Post" }.should_not change(Micropost,
:count)
end
describe "error messages" do
before { click_button "Post" }
it { should have_content('error') }
end
end
describe "with valid information" do
before { fill_in 'micropost_content', with: "Lorem ipsum" }
it "should create a micropost" do
expect { click_button "Post" }.should change(Micropost,
:count).by(1)
end
end
end
...
end
If I run these tests I get the follwing error:
Failures:
1) MicropostPages micropost creation with invalid information should not create a micropost
Failure/Error: expect { click_button "Post" }.should_not change(Micropost, :count)
NoMethodError:
undefined method `[]' for nil:NilClass
# ./app/controllers/microposts_controller.rb:14:in `create'
# (eval):2:in `click_button'
# ./spec/requests/micropost_pages_spec.rb:11:in `block (5 levels) in <top (required)>'
# ./spec/requests/micropost_pages_spec.rb:11:in `block (4 levels) in <top (required)>'
2) MicropostPages micropost creation with invalid information error messages
Failure/Error: before { click_button "Post" }
NoMethodError:
undefined method `[]' for nil:NilClass
# ./app/controllers/microposts_controller.rb:14:in `create'
# (eval):2:in `click_button'
# ./spec/requests/micropost_pages_spec.rb:14:in `block (5 levels) in <top (required)>'
However if I modify the tests and comment out all the #XXX filtering in the Micropost#create action:
def create
#micropost=current_user.microposts.build(params[:micropost])
#Rails.logger.info "hoooola"
#regex=/\A#(\d)+(\w|\-|\.)+/i
#message=#micropost.content.dup
#isResponse=message.match(regex)[0].match(/\d+/)[0]
##micropost.response=isResponse
if #micropost.save
flash[:success]="Micropost created!"
redirect_to root_path
else
#feed_items=[]
render 'static_pages/home'
end
end
The tests pass just fine and the new Micropost is not a Nil object.
It can't seem to find an explanation here.

Answer 1

The error comes from this line:
isResponse=message.match(regex)[0].match(/\d+/)[0]
Check if your two match calls actually match correctly. If the pattern is not found in your string, nil is returned and the [0] call is made on nil. There's two instances in this line alone where this could happen.
Try to spread it out over several lines and check the return values of your matches or extend your Regex to properly check the pattern in one go.