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

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
        [email protected]
        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
        #[email protected]
        #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.

Maybe its the regular expression match(regex)[0].match(/\d+/)[0] that causes the issue... — spas
– spas, Commented Oct 10, 2013 at 11:05
I tried it using irb and It returned the desired ID. Besides, shouldn't it in the worst case just write Nil in the @micropost.response field? — lllllll
– lllllll, Commented Oct 10, 2013 at 11:07
no, because you are accessing it with [0] this will throw the exact same error if the regex doesn't match. — spas
– spas, Commented Oct 10, 2013 at 11:09
oh, you are so righ! It indeed throws the same error when the regex doesn't match. Thank you. If you post an answer I can mark it as correct answer. — lllllll
– lllllll, Commented Oct 10, 2013 at 11:14

KappaNossi · Accepted Answer · 2013-10-10 11:12:06Z

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.

answered Oct 10, 2013 at 11:12

KappaNossi

2,7161 gold badge18 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

lllllll Over a year ago

It seems this is exactly the issue, as also pointed out by @spas. I completely missed that. Also, I wonder what is the appropiate way to debug Controllers. I mean, how would you check the result of each .match if it's inside a controller? I mean I know how to do it in irb, but can't find an appropiate way via testing.

KappaNossi Over a year ago

Well your tests are correctly performing the POST with all form params and your create-action gets executed. You should provide all sorts of input params as you need to expect the users to enter terribly wrong data by accident or sometimes on purpose. Check the results of your tests accordingly. The create call mustn't throw errors for any input. If it does, your validation checks for the correctness of input is not robust enough and you need to add additional conditions. This is not any different from calling your regex match on random values in irb.

lllllll Over a year ago

That makes sense, thanks. Although I was referring to a more explicit debugging à la puts variablename. So I can see actual contents of variables in the terminal.

KappaNossi Over a year ago

Ah sorry. Just printing stuff to the console is very crude by todays standards. You can use the debug logs to print some values. You will need to look up how to use the Ruby Logger (or similar frameworks) yourself though as a simple comment wouldn't be enough to explain. If you have advanced IDEs like RubyMine, you can simply set a breakpoint in your method and then execute arbitrary code when execution stops there when in debug mode.

lllllll Over a year ago

Oh, that's what I thought, only Ruby Logger. I will have to stick to that and keep grep*-ing* the tail of the log/test.log with some keywords. thanks!

Collectives™ on Stack Overflow

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

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related