_why’s metaid gem gives you a metaclass method to explicit access this object:

require 'metaid'
class Person
  def self.oldest
    # find oldest person
  end
end
Person.methods.grep(/oldest/) # => ['oldest']
Person.metaclass.instance_methods.grep(/oldest/) # => ['oldest']

So now here’s a new, fun way to access the metaclass of a class, look for a constant suffixed with ‘Metaclass’. For the Person class, look for PersonMetaclass. Yep, we can have explicit metaclass constants. Or try PersonClass or PersonEigen or PersonEigenclass. No one can agree on what they are called, so I made them all work.

$ gem install magic_metaclass
$ irb

In irb try:

require 'rubygems'
require 'magic_metaclass'
class Person; end
Person
# => Person
PersonMetaclass
# => #<Class:Person>
PersonClass
# => #<Class:Person>
PersonEigenclass
# => #<Class:Person>
PersonEigen
# => #<Class:Person>

Neat.

Finally, the example from above:

class Person
  def self.oldest
    # find oldest person
  end
end
PersonMetaclass.instance_methods.grep(/oldest/) # => ['oldest']

I wrote this gem with no known use cases. If you find any, let me know.

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Chris Shea has come up with GuessMethod – a very cool hack that now deprecates my concept of Magic Wiggly Lines – a spell-checker for runtime code.

What’s it do? Cop a squiz at this genius…

$ gem install guessmethod -y
$ irb
> require 'rubygems'
> require 'guessmethod'
> class Object; include GuessMethod; end  # though this could go in the guessmethod.rb file in the gem
> class Product; def name; "Some product"; end; end
> Prodct.nw.nae
attention: replacing non-existant constant Prodct with Product for Object
attention: sending new instead of nw to Product:Class
attention: sending name instead of nae to #<Product:0x144ff10>:Product
=> "Some product"

That’s going straight into my .irbrc file. My bad spelling, coupled with my British/Australian English, will never slow me down again!

UPDATE: actually, it doesn’t like being in the .irbrc file for Rails console; so in the config/environments/development.rb files will have to do for the moment.

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Keynote

DIY syntax

Dr Nic Academy

I also took the opportunity to introduce Dr Nic Academy – training courses in Ruby on Rails by me. The first course will be 7th and 8th of July in Amsterdam. If you are thinking of attending, hold off buying tickets!! The new website and a special bonus discount price will be coming soon. I’d hate you to miss out.

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The original Dr Nic’s Magic Models were named as such because I entertained the idea of showing them off as a live magic show. So, given 3 minutes in front of some of the Ruby community’s hottest hackers, I got my chance! Not the Original Magic Models, but the never-before-released Magic Model Generator.

How to install and use the magic_model_generator follows the video from RejectConf:

The Magic Show

How to use it

Create a rails application, and point it to your database.

$ rails magic_show -d [mysql|sqlite|postgresql|oracle|etc|etc]
$ cd magic_show
$ cp database.yml.sample database.yml
and point it to your database.yml to your legacy database

I use the database created for the ActiveRecord test cases – activerecord_unittest. If you’ve never downloaded the activerecord gem, run rake build_[mysql|sqlite|postgresql|oracle|etc|etc]_databases, and then rake test_[mysql|sqlite|postgresql|oracle|etc|etc], then you’ve probably got more free time than I do as a result and I appreciate that. And so does my wife.

Now install the magic_model_generator gem:

$ sudo gem install magic_model_generator

Nonetheless, you’re done. That’s all the preparation I did for the video.

Next I recreated the schema.rb file and the schema_info database table via rake db:migrate.

Next I ran the generator:

$ ./script/generate magic_model

And we’re done.

Coming soon

The MMG is awesome.

The one major drawback of the MMG is the same drawback of all rails generators: if you want to regenerate your models (say you update your schema via migrations) then you cannot regenerate your model associations and validations without completely recreating the file, thus destroying anything else you wrote. Which is useless.

The world of version control (subversion, cvs, etc etc) already solved this problem: merging. So I’m investigating adding merging to the rails_generator. That should be neat.

New Gem Generate to get merging too?

Currently the newgem command doesn’t use the rails_generator for creating files. So adding merging to rails_generator won’t help newgem. That is, unless I rewrite newgem. So, I’ll look into that too.

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• What do you think about the current Twitter vs DHH discussion?
• How did you come by with the Magic Model solution?
• What does the New Gem Generator actually do?
• Will we see ‘Rails Distros’ in the long run?
• Where are you from? What’s your current day job, is it Rails related? And what’s your history with Rails?
• Did you get your free t-shirt?

Brazilian Fabio Akita – author of the first Brazilian book on Ruby on Rails also wanted to know, so he asked.

Thanks to my friend Carlos Eduardo for teeing it up.

Go to interview

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At this point in time there’s no facility in Rails to talk to more than one database at a time.

Alex Payne

I possibly have such a facility. Perhaps it will help, and I will get some DHH-love and perhaps a free Twitter account for my troubles. Or perhaps a t-shirt.

As a bonus, the solution even includes decent Ruby-fu syntax. So, if you’re just here for the view:

class PeopleController < ApplicationController
  def index
    @people = conn::Person.find(:all)
  end
end

That code just there solves all our problems. It will invoke Person.find(:all) on a random database connection to (assumably) a clone database. Awesomeness I think. I hope it helps Twitter and all the Twit-sers (or whatever you call a user of Twitter).

This solution comes from the magic_multi_connections gem.

What is going on here?

I think a tutorial is the best way to demonstrate what is happening here. So, let's create a rails app and mix in the magic_multi_connections gem.

First, get the gem. Second, create a rails app:

$ sudo gem install magic_multi_connections
$ rails multi -d sqlite3

Now edit the config/database.yml file to create some more databases:

development:
  adapter: sqlite3
  database: db/development.sqlite3
  timeout: 5000

development_clone1:
  adapter: sqlite3
  database: db/development_clone1.sqlite3
  timeout: 5000

development_clone2:
  adapter: sqlite3
  database: db/development_clone2.sqlite3
  timeout: 5000

But please pretend these are uber-MySQL clusters or whatever.

Think of :development as the read-write connection, and the :development_cloneN connections are for read-only access.

At the bottom of your environment.rb file, add the following:

require 'magic_multi_connections'
connection_names = ActiveRecord::Base.configurations.keys.select do |name|
  name =~ /^#{ENV['RAILS_ENV']}_clone/
end
@@connection_pool = connection_names.map do |connection_name|
  Object.class_eval <<-EOS
    module #{connection_name.camelize}
      establish_connection :#{connection_name}
    end
  EOS
  connection_name.camelize.constantize
end

Let's test what this gives us in the console:

$ ruby script/console
>> @@connection_pool
=> [DevelopmentClone1, DevelopmentClone2]
>> DevelopmentClone1.class
=> Module
>> DevelopmentClone1.connection_spec
=> :development_clone1

Our new modules will act as connections. One module per connection. The code above gives them names to match the connection names, but its really irrelevant what they are called, thanks to the mysterious conn method.

So, go create some models and some data. I'll use Person as the class here.

To setup the schemas in our clone databases, we'll use rake db:migrate. To do this:

$ cp config/environments/development.rb config/environments/development_clone1.rb
$ cp config/environments/development.rb config/environments/development_clone2.rb
$ rake db:migrate RAILS_ENV=development
$ rake db:migrate RAILS_ENV=development_clone1
$ rake db:migrate RAILS_ENV=development_clone2

To differentiate the databases in our example, assume there are two Person records in the :development database, and none in the two clones. Of course, in real-life, they are clones. You'd have a replicate mechanism in there somewhere.

Now, we can access our normal Rails modules through our connection modules. Magically of course.

>> ActiveRecord::Base.active_connections.keys
=> []
>> Person.count
=> 2
>> ActiveRecord::Base.active_connections.keys
=> ["ActiveRecord::Base"]
>> DevelopmentClone1::Person.count
=> 0
>> ActiveRecord::Base.active_connections.keys
=> ["ActiveRecord::Base", "DevelopmentClone1::Person"]

Wowzers. Person and DevelopmentClone1::Person classes?

But note - Person.count => 2 and DevelopmentClone1::Person.count => 0 - they are accessing different databases. The same class definition Person is being used for multiple database connections. We never defined more Person classes. Just the standard default one in app/models/person.rb.

The active_connections result shows that DevelopmentClone1::Person has its own connection. Yet you never had to manually call DevelopmentClone1::Person.establish_connection :development_clone1 - it was called automatically when the class is created.

Of course, DevelopmentClone2::Person is automatically connected to :development_clone2, and so on.

Behind the scenes

Let's look at our generated classes:

$ ruby script/console
>> DevelopmentClone1::Person
=> DevelopmentClone1::Person
>> Person
=> Person
>> DevelopmentClone1::Person.superclass
=> Person

That is, there is a DevelopmentClone1::Person class, automagically generated for you, which is a subclass of Person, so it has all its behaviour etc.

Dynamic connection pools within Rails controllers

The magic of the conn method will now be revealed:

$ ruby script/console
>> def conn
>>   @@connection_pool[rand(@@connection_pool.size)]
>> end
>> conn::Person.name
=> "DevelopmentClone2::Person"
>> conn::Person.name
=> "DevelopmentClone1::Person"

The conn method randomly returns one of the connection modules. Subsequently, conn::Person returns a Person class that is connected to a random clone database. Booya. Free Twitter swag coming my way.

Place the conn method in the ApplicationController class, and you can get dynamic connection pooling within Rails actions as needed, as in the following example (from the top of the article):

class PeopleController < ApplicationController
  def index
    @people = conn::Person.find(:all)
  end
end

Decent Ruby-fu, I think. Certainly better than manually calling establish_connection on model classes before each call (or in a before_filter call, I guess).

This is just a concept

I know this tutorial above works. But that might be the extent of what I know. Let me know if this has any quirks (especially if you solve them), or if this is a stupid idea for implementing connection pooling with nice Ruby syntax.

Hope it helps.

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Its like coming home and dinner is already cooked for you.

Its like being good looking and funny.

But this is Ruby, so we call it Magic!

With the release of 0.9.1, you can configure how much cheating, lying and thievery – err, magic – you want.

Already got model classes, but you haven’t gotten around to writing validations for some of them?

class Person < ActiveRecord::Base
  generate_validations
end

As always, if you don't have a Person class, you'll get it for free plus validations.

As always, with automatically created classes AND pre-existing classes, if your schema supports an association and you ask for it it will be there. If you don't want a certain association to exist in your application... don't ask for it. The Magic Models are no place for enforcing law and order.

The other publicly announced, above board, for-sale to the general public feature you might like to know about is Magic Modules.

You can now use modules to specify common features of magic models. Currently supported is table name prefixes. If you need anything else, ask.

module Admin
  magic_module :prefix_table_name => 'admin_'
end

Admin::Permission.table_name # => 'admin_permissions'

The upcoming Magic Multi-Connections use this same concept to allow modules to specify different database connections instead of using superclasses. All this and more in the Magic Models: Spring collection series.

The end.

Ok, there's more. Secret stuff. Backdoor hooks into a Harry Potter world of mystery. Ways to execute code, import modules, and what-not upon newly created magic models. Awesome magicalness.

But you'll need to read the code to find them, and have some imagination as to what you'd want to dynamically do to your generated classes.

But as an example to prod your brain. Our schema at work supports date-ranging on many tables. The table will have a primary id key, plus another primary key - effective_start_date. All these tables end with the suffix '_history'. So when a new model class is created, I use the hooks to test the table name suffix, and if table_name =~ /_history$/ then I include a module that adds more methods etc to these date-ranged classes.

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Magic Models 0.8.0 exhibited range of wacky behaviour and I’ve been suggesting people 0.7.2 for a long time, instead of releasing 0.9.0, which I mostly wrote last year.

I received a huge patch for Composite Primary Keys in my inbox in February and despite the emails of “when will this patch be released” by the punters, I sat on it.

I’ve also mentioned in emails several new projects that I’ve either never released or they are lurking on RubyForge without any celebratory fanfare. For example, the Magic Model Generator – got 200 tables in a legacy schema? Generate 200 model files in 20 seconds.

The share price has now plummeted, and over Easter I bought back all the shares at half price. All that’s left to do now is unveil a barrage of new projects and releases and watch the share price soar. Booya.

So, over the next week or so, you will be treated to:

So call the babysitter, grab yourself a champagne, and find a seat in front of the catwalk: its show time.

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I’ll write a separate post on Ola’s presentation shortly. It was awesome and I videoed it. Hehehe.

But first and foremost, lets talk about me. Or rather, let’s talk about my talk, which was also videoed.

Meta-magic in Ruby
- Weaponry.pdf

Meta-magic in a programming language is as important to programmers as changeable ring tones are to teenagers. Authors of programming languages cannot provide every feature to everyone, so it is so wonderful to be able to add new language features and extensions that you want. Everyone knows you can add Jessica Simpson as your mobile ring tone, but not all programmers know that you can add new features to their programming world.

So here is an overview to a new world of happiness. It also overviews how the Magic Models work, and introduces a new gem I’m working on – the Magic Wiggly Lines – described as “genius or insane”

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I have suggested I’d release 0.9 many times on Google Groups.

You see sentences like this in many many blogs. I have empathy for the authors who diligently markup each word with a different URL, but it is a wonderful way to describe and hyperlink in a meaningful way.

In the above fabricated, never-before-published quote, all the links are from a Google Groups search. So I knew I’d want to auto-generate it, because the mere thought of manual labour drives me to automation.

This resulted in the new sentence_with_links gem (I like bundling small chunks of code in new gems instead of stand alone library files so that the README file and test cases are encapsulated with the library code).

Installation

> gem install sentence_with_links

Usage

That is, String now has a with_links method, that generates the HTML as above. What if there are more links than words in the sentence? See the “Jessica Simpson” image search example below.

Mashup with Google Groups

For the above demonstration, let’s use our handy Hpricot parser to scrape the GoogleGroups search results, and .

Mashup with Google Images using JSON API

Demo: There are many Jessica Simpson images on Google
(also here, here, here, here, here, here, here, here, here, here, here, and here).

Note how the with_links function handles more links than sentence words? It appends a multitude of ‘here’ links. If you can think of more pleasurable alternatives, let me know. Either way, we don’t want to miss out on any important Jessica Simpson images. They are all there.

Instead of HTML, let’s parse some JSON returned by Google’s alter-ego search interface SearchMash, which provides a JSON API.

First, get the JSON Ruby parser:

gem install json

Then slap it all together…

And there you have it, sentences with links, the lazy Ruby way.

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