Learning Rails

Classifying Users

Most applications have at least two categories of users—administrators and ordinary users. Many applications have finer-grained permissions, but this is a good place to start. Code for this is available in ch14/students008. The first step toward creating an extra category of users is to create a migration with a suitable name:

script/generate migration AddAdminFlagToUsers

In the newly created migration, under db/migrate, change the migration file with the name ending in add_admin_flag_to_users so that it looks like Example 14-4.

Example 14-4. A migration for adding a boolean administration flag to the users table

class AddAdminFlagToUsers < ActiveRecord::Migration
  def self.up
    add_column :users, :admin, :boolean, :default => false, :null => false
  end

  def self.down
    remove_column :users, :admin
  end
end

This adds one column to the users table, a boolean named admin. It defaults to false—most users will not be administrators—and can’t have a null value. Run rake db:migrate to run the migration and add the column.

Next, there’s a small challenge. The system really should have at least one administrator, but building a complete user administration facility means building another whole set of forms and controller methods. In addition, it probably makes sense to be able to designate an initial user as administrator before locking all nonadministrators out of the user management system.

For this demonstration, there’s an easy answer—the Rails console. In addition to its use in ...