URLS

  http://rubyforge.org/projects/codeforpeople/
  http://codeforpeople.com/lib/ruby/traits

INSTALL

  yes|sudo gem install traits

ABOUT

  traits.rb is set of attr_* like methods on steroids, caffeine, and botox.
  it encourages better living through meta-programming and uniform access
  priciples. traits.rb supports smart inheritence of class attributes and a
  fistful of hooks for veryifying and munging attr values.

VERSION

  0.10.0

HISTORY

  0.10.0
    - removed use of additional instance var to denote whether a value had
      been set.  now the test is only 'defined? @#{ name }'.

  0.9.2
    - fixed a bug where list traits, for example

        trait 'letters' => %w[ a b c ]

      were flattened in a way that exploded trait initialization

    - streamlined TraitInit module

    - added OpenTraits class and otraits method

        conf = otraits{
          port 42
          host 'forty-two'
        }
        p conf.port            #=> 42
        p conf.host            #=> 'forty-two' 
        conf.username 'zaphod'
        p conf                 #=> {"username"=>"zaphod", "port"=>42, "host"=>"forty-two"} 

  0.9.0
    - luke kaines made quite a few suggestions and bug reports that enabled this
      release including making a few methods indifferent about string/symbol
      args/keys and the introduction of a simple method 'trait_init' that can be
      used to create keyword based initializers, eg:

        require 'traits'

        class C
          include TraitInit

          trait :a, :type => Integer
          trait :b, :type => Integer

          def initialize opts = {}
            trait_init opts
          end
        end

        C::new :a => 4, :b => 2

  0.8.0
    - traits now supports a whole slew of hooks that can be registered to fire
      pre or post setting an attribute, to cast a value to another type, to
      munge a value destructively, to require only certain types, to require a
      certain ducktype signature, and to validate arguments passed.  check out
      sample/m.rb, sample/n.rb, or sample.o.rb to see it in action.  the
      mechanism is quite flexible allowing method names, lambdas of varying
      arity, and lists of either/or to be passed to any hook.

    - you can find a gem for trais on codeforpeople - but i've still not coded
      up automated updating from codeforpeople to rubyforge so it won't show up
      as a remote gem yet.

  0.7.0
   - patched in the support i had written eariler for 'hooks' to be called
     pre/post setting a trait. plus shortcut to 'validate' traits which simply
     sets up a 'pre' hook which is used as a predicate.  eg:

        class C; trait 'number', 'validate' => proc{|n| Numeric === n}

     pre and post hooks are used in the same way, eg:

        class C
          trait 'a', 
            'pre' => proc{|val| p "#{ val } to set with"},
            'post' => proc{|val| p "#{ val } set"},
        end

     but the really cool thing is that all of these blocks are both passed the
     value in question but also evaluate with 'self' set appropriately.  eg

        class Car
          positive_int = lambda{|n| Fixnum === n and n > 0}
          legal = proc{|s| s < speed_limit}

          trait 'speed_limit', 'validate' => positive_int, 'default' => 42
          trait 'speed', 'validate' => legal
        end

        c = Car::new
        c.speed = 115

      works as you'd expect:

        (eval):14:in `speed=': validation of speed=(115) failed! (ArgumentError)
                from a.rb:13

  0.6.0
    - fixed bug in where a default trait given as an empty array, eg:

        class C;  has 'a' => [];  end

      was exploded into the empty list when passed to the setter to initialize
      the default value.

  0.5.0
    - general code cleanup

  0.4.0
    - tweaked writer code so multiple values can be passed to setters
    - tweaked method of running blocks to use instance_eval so explicit 'this'
      arg is no longer needed (though it can still be used)

  0.3.0
    added ability of default values to be specified with block for deferred
    context sensitive initialization (see sample/c.rb)

  0.1.0

    completely reworked impl so NO parsing of inspect strings is required -
    it's all straight methods (albeit quite confusing ones) now.  the
    interface is unchanged.

  0.0.0

    initial version


AUTHOR

  ara [dot] t [dot] howard [at] noaa [dot] gov

SAMPLES

  @samples

CAVEATS

  this library is experimental and subject to change - though it has not for
  several versions and much of my code hinges is on it now so you can expect the
  interface to be stable in the near future - the only changes planned are those
  that fix bugs or add features.

LICENSE

  same as ruby's