After 6 month I've released a new version of Simple Descriptor.
This gem makes possible to attach some extra informations to a generic ruby class, but its mission is now includes specific methods to allow more control and flexibility on ActiveRecord validations, in addition to this, Simple Descriptor may help you in building a consistent approach in areas where rails doesn't.
Let's start getting our hands dirty, first of all install the gem
sudo gem install simple_descriptor
after that you need to require the gem i.e in your config/environments.rb file
require 'simple_descriptor'
now let's tweak our Employee ActiveRecord model
the migration to create the Employee model will be
class CreateEmployees < ActiveRecord::Migration
def self.up
create_table :employees do |t|
t.column :first_name, :string, :limit => 30, :null => false
t.column :middle_name, :string, :limit => 10, :null => true
t.column :last_name, :string, :limit => 30, :null => false
t.column :gross_wage, :integer, :null => false
t.column :personal_email, :string, :limit => 100, :null => false
end
end
def self.down
drop_table :employees
end
the basic model definition will be
class Employee < ActiveRecord::Base
end
to get some validations for free we need to add 2 lines of code
class Employee < ActiveRecord::Base
extend SimpleDescriptor::ClassDescriptor
validates_ar_descriptions
end
These 2 extra lines will
- validates_presence_of every field defined as NOT NULL
- validates_length_of every field defined with a limit
- validates_numericality_of every field defined as anumber
but there some extra as well, fire the console of your rails app and type
Employee.described_as :string
this will return all the fields defined as string in the database.
Now always in the console try
Employee.maxlegth(:first_name)
this will return 30 which is the maximum length of the first_name field
Or again you can have the list of the required fields
Employee.described_as :required
=> [:first_name, :gross_wage, :last_name, :personal_email]
Or you can ask your model if specific field is required
Employee.describes? :first_name as => :required
=> true
If you want to inspect a bit more what's happening behind the scenes you can use
Employee.descriptions
Now, let's say you have some different models i.e. Employee, Manager, Consultant and in all these models you have some sensible fields you want to show only to authorized people.
If you use Simple Descriptor for all these models you can easily define which fields contains sensible informations, for the Employee it would be
class Employee < ActiveRecord::Base
extend SimpleDescriptor::ClassDescriptor
validates_ar_descriptions
describe :gross_wage as => :sensible
end
Starting from this moment you can ask the Employee class if a field is sensible or not
Employee.describes? :gross_wage, :as => :sensible
=> true
Employee.describes? :first_name, :as => :sensible
=> false
Or you can obtain the list of sensible fields
Employee.described_as :sensible
=> [:gross_wage]
This may help you to manage sensible data show rules in your views or in your controller.
To know more about Simple Descriptor you can just visit the online
docs
