api 笔记

  class Customer < ActiveRecord::Base
    attr_accessible :name, :nickname
  end

  customer = Customer.new(:name => "David", :nickname => "Dave", :credit_rating => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { :name => "Jolly fellow", :credit_rating => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average"

class Customer < ActiveRecord::Base
    attr_protected :credit_rating
  end

  customer = Customer.new("name" => David, "credit_rating" => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { "description" => "Jolly fellow", "credit_rating" => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average

class CreditCard < ActiveRecord::Base
    # Strip everything but digits, so the user can specify "555 234 34" or
    # "5552-3434" or both will mean "55523434"
    def before_validation_on_create
      self.number = number.gsub(/[^0-9]/, "") if attribute_present?("number")
    end
  end

  class Subscription < ActiveRecord::Base
    before_create :record_signup

    private
      def record_signup
        self.signed_up_on = Date.today
      end
  end

  class Firm < ActiveRecord::Base
    # Destroys the associated clients and people when the firm is destroyed
    before_destroy { |record| Person.destroy_all "firm_id = #{record.id}"   }
    before_destroy { |record| Client.destroy_all "client_of = #{record.id}" }
  end