This lab requires some setup so run this in your terminal

createdb dynamic_orm_test
createdb dynamic_orm_development
psql -f spec/db/programmer_seed.sql -d dynamic_orm_development
psql -f spec/db/state_seed.sql -d dynamic_orm_development

This will create a test and development database you can poke around in with rake console.

Points of interest

Be sure to checkout the files in spec/db/. They have the seed data for the tests.

The Inflecto gem will help you with pluralizing and singularizing words. Docs here

You'll be building your own ORM. The class you will be building is Base located inside the FlactiveRecord module.

module FlactiveRecord
  class Base
  end
end

All of the classes that inherit from your ORM will have the following class methods:

• .all
• .column_names
• .connection
• .exec
• .find
• .table_name

The instance methods will be created dynamically based on the column names. A Programmer instance will have the following methods:

• #id
• #id=
• #language
• #language=
• #name
• #name=

You will find 2 classes defined in the tests

class State < FlactiveRecord::Base
end

class Programmer < FlactiveRecord::Base
end

DO NOT MODIFY THESE CLASSES. All functionality will be added by inheriting from FlactiveRecord::Base

SELECT column_name
FROM information_schema.columns
WHERE table_name='#{table_name}'

Whenever a class is inherited, ruby calls the superclass' self.inherited method and passes it the class that inherited it.

class SoSuper
  def self.inherited(base)
    puts "#{base} inherited #{self}"
  end
end

class NotSuper < SoSuper
end
#=> NotSuper inherited SoSuper

Notice that inside the inherited class, self is SoSuper. We can change self to be the inherited class by using .class_eval

class SoSuper
  def self.inherited(base)
    puts "self is the class #{self}"
    base.class_eval do
      puts "self is the class #{self}"
    end
  end
end

class NotSuper < SoSuper
end
# => self is the class SoSuper
# => self is the class NotSuper

Use our DBConnection object to run sql commands.

In your Base class you can wrap your methods using

def self.exec(sql, args=[])
  DBConnection.instance.exec(sql, args)
end

def self.connection
  DBConnection.instance.connection
end