NAME
  attributes.rb

INSTALL
  gem install attributes

URIS
  http://codeforpeople.com/lib/ruby
  http://rubyforge.org/projects/codeforpeople/
  http://codeforpeople.rubyforge.org/svn/

SYNOPSIS
  attributes.rb provides a set of attr_* like method with several user
  friendly additions.  attributes.rb is similar to the traits.rb package but
  sacrifices a few features for simplicity of implementation.

  the implementation of attributes.rb borrows many of the best ideas from the
  metakoans.rb ruby quiz

    http://www.rubyquiz.com/quiz67.html

  in particular the solutions of Christian Neukirchen and Florian Gross along
  with concepts from the original traits lib

  key features provided by attributes are

    - ability to specify default values for attrs and definition time.  values
      can be literal objects or blocks, which are evaluated in the context of
      self to initialize the variable

    - classes remember which attributes they've defined and this information is
     available to client code

    - a whole suite of methods is defined by calls to #attributes including
     getter, setter, query (var?) and banger (var! - which forces
     re-initialization from the default value)

    - ability to define multiple attributes at once using key => value pairs

    - fast lookup of whether or not a class has defined a certain attribute

    - attributes can be defined on objects on a per singleton basis as well

    - getters acts as setters if an argument is given to them

    - block caching, calling an attribute with a block sets the instance
      variable to that block

  all this in < 100 lines of code

HISTORY
  5.0.0
    - added support for block caching. for example

        - simple block caching:

            class Filter 
              attribute :process
            end

            filter = Filter.new

            filter.process{|line| line.upcase}

            lines.each do |line|
              p filter.process.call(line)
            end

        - using block caching to delay block evaluation/class-factory:

            module MigrationDSL
              attribute :migration

              def migration_class
                model = self

                Class.new(::ActiveRecord::Migration) do
                  singleton_class =
                    class << self
                      self
                    end
                  singleton_class.module_eval{ attribute :model => model }
                  singleton_class.module_eval &model.migration
                end
              end
            end

            class Table < ActiveRecord::Base
              extend MigrationDSL
            end

            class Jobs < Table
              migration do
                def up
                  create_table model.table_name, :primary_key => model.primary_key do |t|
                    t.column 'vinyl_shoes', :text
                  end
                end

                def down
                  create_table model.table_name
                end
              end
            end

            ...

            JobsMigration = Jobs.migration_class

  4.1.0
    - 4.0.0 introduced a bug where a query (foo?) would not initialize a var -
      4.1.0 fixes that

  4.0.0
    - removed dependancy on, and bundle of, pervasives
    - faster.  as fast as normal method definition.
    - faster lookup for MyClass.attributes.include?('foobar')

  3.7.0
    small patch to use 'instance_variable_defined?' instead of defined?
    keyword
  
  3.5.0
    migrated to a pervasives based impl to attributes should work on any
    object - even blankslate objects

  3.3.0

    moved to an instance variable-less model using an module level closure for
    the attributes list

SAMPLES
  @samples