Ruby 1.9 | Closer to Code

First of all I will point one thing: I'm not a professional book reviewer. I don't do this too often. Probably because I don't have enough time. However, I've decided to do a review of "Learning Mongoid" because I wanted to learn something new and Packt Publishing was kind enough to lend me a copy for this review. So here it is. I'll start with things that I really liked. As usual, there were some things that could be corrected, but if you have Rails experience, this book will be really helpful for you.

Things I did like about this book

It's not extremely long

You may consider this an issue, but I've found this really helpful. Chapters aren't long, so getting through them is not painful. I bet you've sometimes wondered "what is the author getting at?". Not with this one. Chapters (and the book itself) are really consistent. You won't get bored reading this one or feel like giving up.

A lot of examples

I don't like theoretical texts and books, without any examples of good practices. We're developers, we should be able to play around with new stuff that we learn! And one of the things that I really liked about Learning Mongoid is that I was able to copy-paste almost every example and play-around with it on my computer.

Field aliases

Even now I can recall times, where I had to rename fields, so I would be able to create an index for them :). I don't know why, but this is not a thing that is covered in tutorials or other books (at least not in those that I know). On the other hand this is super useful. I was really surprised to see this one here. It made me realize one thing - this book was written by other guys who develop Rails-Mongoid software.

Geospatial searches and querying in general

When doing a lot of Geolocalization stuff - Mongo can be really helpful and can simplify a lot of things. All basic geo-search options are covered in this book. In general, the whole querying chapter is well-written and together with aggregation framework, it covers all common cases that you may want to use.

Performance tuning and maintenance

Performance is really important. If you don't do it right, you might end up with really slow application. This book covers the basics of both - performance tuning and Mongoid maintenance, so after reading it you will be able to use some of Mongo and Mongoid properties to gain few seconds of users life ;)

Things I didn't like about this book

A good book - but not sure whether or not for pros or beginners

Learning Mongoid by Packt Publishing is a solid book about Mongoid, although it lacks some information that would be super useful for beginners. I've got a feeling that it covers most of "stuff you need to know to start working with Mongo and Mongoid", but as mentioned above, when it comes to people who want to start using Mongoid and they know only a bit about Ruby - it can be harsh.

Install RVM - but do this on your own

I know that this book should be (and it is!) about Mongoid, but since we're talking about it, it is worth at least mentioning how to install RVM, especially because it is one of the prerequisites. 1-2 pages about RVM would be really helpful.

Need some config hints? Well not this time

The second thing that is lacking is a Mongoid setup instruction. Not even a word on what should/should not be in mongoid.yml, what are the most important options, etc. There is even mention of it in the book:

There are entirely new options in mongoid.yml for database configuration

Although none of the changes are listed. No information about replica_set, allow_dynamic_fields, preload_models or any other important setup options. This is a must be in any good Mongoid book.

Want to upgrade to most recent Mongoid version? We won't help you out :(

I've mentioned that below, but I will point it out again. Authors say, that there are several differences between new and old Mongoid, although they don't list them (except IdentityMap). I think they should.

Want to migrate your app to Mongoid?

Maybe you want to move your app from ActiveRecord to Mongoid (I did it few times myself)? If so, "Learning Mongoid" will help you handle Mongo part, but it won't help you with the migration process itself. Sodibee (example book app) is a Mongoid base app. Maybe authors assumed, that if you master ActiveRecord and Mongoid, you don't need any extra help to switch between them...

Summary

Would I recommend this book? Yes - I already have! It can be a solid Mongo and Mongoid starting point for begginers (apart some issues that I've mentioned) and a "knowledge refresher" for people that use Mongoid longer that few weeks. It is well written and it has a lot of examples. Really a good one about Mongoid.

If you're interested in buying this book, you can get it here.

Few days ago, I've decided to get back to the "original" Paperclip. Until now, in one of my projects I've been using forked version with additional tweaks. However, supporting it for 3 years was enough. Getting back on track was fairly simple. It took me 1 day to fix the file structure, next day to rewrite validators and that would be all except one thing. Paperclip attaches error to 3 fields (example for thumb file):

thumb_file_name
thumb_file_size
thumb_content_type

I don't like this idea, since those are basically the internals of Paperclip implementation and in my opinion, all the errors should be attached to the "base" attribute (which in this case is called thumb). Furthermore this is not only the architectural problem but it also affect my views. I use Bootstrap with a SimpleForm attached to it and adding Paperclip to it seams fairly simply:

= simple_form_for @user, :html => { :class => 'form-horizontal' } do |f|
  = f.input :avatar

And... this should be it. However, as I mentioned above, Paperclip attaches errors to fields different than "thumb" (not all of them but it doesn't matter), so they aren't displayed on the interface. I could use something like that:

= f.errors :thumb_content_type

and well, this indeed works, unfortunately without any Bootstrap stylings. Also it requires extra line for each attachment that I use. So it sucks! That's why I've decided to do a little hack on it: let's just copy all the error messages into original "base" attachment name. This should solve our problem (and it did):

# lib/paperclip_extensions.rb
module PaperclipExtensions

  extend ActiveSupport::Concern

  module ClassMethods
    # Changes the default Paperclip behaviour so all the errors from attachments
    # are assigned to an attachment name field instead of 4 different once
    # This allows us to use Bootstrap and SimpleForm without any other extra
    # code
    def has_attached_file(name, options = {})
      # Initialize Paperclip stuff
      super
      # Then create a hookup to rewrite all the errors after validation
      after_validation do
        self.errors[name] ||= []
        %w{file_name file_size content_type updated_at}.each do |field|
          field_errors = self.errors["#{name}_#{field}"]
          next if field_errors.blank?

          self.errors[name] += field_errors
          field_errors.clear
        end
        self.errors[name].flatten!
      end
    end
  end

end

ActiveRecord::Base.send(:include, PaperclipExtensions)

Just put this code into a file in lib/ and create an initializer where you will require it:

# config/initializers/paperclip_extensions.rb
require 'paperclip_extensions'

After that, you are ready to go :) Enjoy using Paperclip with Bootstrap and SimpleForm without any problems!

Tag: Ruby 1.9

Learning Mongoid – Build scalable, efficient Rails web applications with Mongoid – Book review