4. Метапрограмиране

4. Метапрограмиране

class << selfspeaker "Стефан Кънев"speaker "Николай Бачийски"on_date "20‐10‐2008"

end

lectures.last.recap

class Vectordef initialize(x, y, z)@x, @y, @z = x, y, z

end

def length(@x * @x + @y * @y + @z * @z) ** 0.5

end

def to_s() “(#@x, #@y, #@z)” endend

orientation = Vector.new 1.0, 0.0, 1.0puts orientation.length

class Vectorattr_accessor :x, :y, :z

def initialize(x, y, z)@x, @y, @z = x, y, z

endend

class Vector

def +(other)Vector.new self.x + other.x,

self.y + other.y,self.z + other.z

end

def *(n)Vector.new @x * n, @y * n, @z * n

end

end

class Fixnumalias broken_equal? ==

def ==(other)if (self.equal?(0) and other.equal?(1)) or

(self.equal?(1) and other.equal?(0))true

elseself.broken_equal?(other)

endend

end

pesho = Coin.new 0.50

def pesho.pick_up(person)person.get_hopes_highperson.humiliateperson.make_sad

end

metaprogramming.inspect

class Student < ActiveRecord::Basevalidates_presence_of :name, :fn, :emailvalidates_numericality_of :fnvalidates_email :email

belongs_to :universityhas_many :gradeshas_many :courses, :through => :courseshas_and_belongs_to_many :groups

before_destroy do |student|InformationMailer.deliver_destroyed(student)

endend

html :xmlns => "http://www.w3.org/1999/xhtml" dohead dotitle "Registered students"style :type => "text/css" do

content "* { font‐family: Verdana; }"end

endbody doh1 "Registered studentsul do

@students.each do |student|li dop student.nameunless student.url.nil?

a "Personal website", :href => student.urlend

endend

endend

end

class Person; endclass Programmer < Person; endclass Rubyist < Programmer; end

>> chunky = Rubyist.new>> chunky.classRubyist>> chunky.class.superclassProgrammer>> chunky.class.ancestors[Rubyist, Programmer, Person, Object, Kernel]>> chunky.instance_of?(Rubyist), chunky.instance_of? Programmer[true, false]>> chunky.kind_of?(Rubyist), chunky.kind_of?(Programmer)[true, true]>> Rubyist < Person, Rubyist < Programmer, Person < Rubyist[true, true, false]

respond_to?

class Vectordef initialize(x, y, z) @x, @y, @z = x, y, z enddef length() (@x * @x + @y * @y + @z * @z) ** 0.5 enddef method_missing(name, *args)

return Vector.new(‐@x, ‐@y, ‐@z) if name.to_sym == :invertsuper

endprivatedef sum() @x + @y + @z end

end

>> vector = Vector.new 1.0, 2.0, 3.0>> vector.respond_to? :lengthtrue>> vector.respond_to? :invertfalse>> vector.respond_to? :sumfalse>> vector.respond_to?(:sum, true)false

class Vectorattr_accessor :x, :y, :zdef initialize(x, y, z) @x, @y, @z = x, y, z end

end

>> vector = Vector.new 1.0, 2.0, 3.0>> vector.instance_variable_get :@y2.0>> vector.instance_variable_set :@y, 5.05.0>> vector.instance_variable_get :@y5.0>> vector.y5.0>> vector.instance_variables["@z", "@y", "@x"]

public_methods(all=true)protected_methods(all=true)private_methods(all=true)

methods

>> vector = Vector.new 1.0, 2.0, 3.0>> vector.methods["inspect", "taguri", "clone", "public_methods", "taguri=", "display", "method_missing", "instance_variable_defined?", "equal?", "freeze", "methods", "respond_to?", "dup", "instance_variables", "__id__", "method", "eql?", "id", "singleton_methods", "send", "length", "taint", "frozen?", "instance_variable_get", "__send__", "instance_of?", "to_a", "to_yaml_style", "type", "protected_methods", "instance_eval", "object_id", "require_gem", "==", "require", "===", "instance_variable_set", "kind_of?", "extend", "to_yaml_properties", "gem", "to_s", "to_yaml", "hash", "class", "private_methods", "=~", "tainted?", "untaint", "nil?", "is_a?“]>> vector.public_methods(false)["method_missing", "length"]

method(:length)

>> v1 = Vector.new 1.0, 0.0, 0.0>> v2 = Vector.new 0.0, 3.0, 4.0>> length = v1.method(:length)>> puts length[]1.0>> unbinded = length.unbind>> unbinded.bind(v2)[]5.0

Vector.instance_method(:length)

class Coin

def initialize(value)@value = value

end

def pick_up(person)person.enrich self.value

end

def put_on_train_rail!self.flatten

endend

pesho = Coin.new 0.50gosho = Coin.new 1.00

pesho@value = 0.50

gosho@value = 1.00 Coin

pick_up(person)put_on_train_rails()


end

def pesho.flip:heads

end

singleton_methods

>> pesho.singleton_methods["pick_up", "flip“]

pesho@value = 0.50

gosho@value = 1.00 Coin

pick_up(person)put_on_train_rails()

pesho` < Coinpick_up(person)

flip()


end

class << peshodef pick_up(person)person.get_hopes_highperson.humiliateperson.make_sad

endend

class << peshoattr_accessor :valuealias take_from_ground pick_up

end

>> pesho.value0.50>> pesho.take_from_ground(stefan):(

>> singleton_class = class << peshoself

end>> p pesho#<Coin:0x3ec5cf4 @value=0.50>>> p singleton_class#<Class:#<Coin:0x3ec5cf4>>>> p singleton_class != pesho.classtrue

class Objectdef singleton_classclass << selfself

endend

end

>> pesho.singleton_class

>> x, y = 5, 10>> code = "x + y">> sum = eval(code)>> puts sum15>> eval "def square(x) x ** 2 end">> puts square(10)100

instance_eval

>> v = Vector.new 1.0, 2.0, 3.0>> v.instance_eval "@x + @y + @z"6.0>> v.instance_eval { @x + @y + @z }6.0

class_eval

>> v = Vector.new 1.0, 2.0, 3.0>> Vector.class_eval "def sum() @x + @y + @z end">> p v.sum6.0>> Vector.class_eval do

def sum()@x + @y + @z

endend

>> p v.sum6.0

def add_name_method(klass, given_name)klass.class_eval do

def namegiven_name

endend

end

>> add_name_method(Vector, "I, Vector")>> v = Vector.new 1.0, 2.0, 3.0>> p v.nameundefined method `given_name' for Vector

define_method

def add_name_method(klass, given_name)klass.send(:define_method, :name) do

given_nameend

end

>> add_name_method(Vector, "I, Vector")>> v = Vector.new 1.0, 2.0, 3.0>> p v.name"I, Vector"

Module

namespacemix‐in

namespace

module PseudoMathclass Vector

def initalize(x, y) @x, @y = x, y endend

def PseudoMath.square_root(number)number ** 0.5

end

PI = 3.0end

puts PseudoMath::PIheight = PseudoMath::Vector.new 3.0, 4.0puts PseudoMath::square_root(5)puts PseudoMath.square_root(5)

mix‐in

module Debugdef who_am_i?

"#{self.class.name} (\##{self.object_id})" +" #{self.to_s}"

endend

class Coininclude Debug

end

>> coin = Coin.new>> puts coin.who_am_i?Coin (#33139900) #<Coin:0x3f35978>

>> pesho = Coin.new>> pesho.extend(Debug)>> puts Coin.who_am_i?Coin (#33139900) #<Coin:0x3f35978>

Умни константи

module Unicodedef self.const_missing(name)

if name.to_s =~ /^U([0‐9a‐fA‐F]{4,6})$/utf8 = [$1.to_i(16)].pack('U')const_set(name, utf8)

elseraise NameError, "Unitinitialized constant: #{name}"

endend

end

puts Unicode::U00A9puts Unicode::U221Eputs Unicode::X

Генериране на XML

XML.new(STDOUT) dohtml do

head dotitle { "Extrapolate me" }

endbody(:class => 'ruby')

endend

class XMLdef initialize(out, indent=' ', &block)

@res = out@indent = indent@depth = 0self.instance_eval(&block)@res << "\n"

end

def tag(name, attributes={})

?end

alias method_missing tagend

def tag(name, attributes={})@res << "<#{name}"attributes.each { |attr, value| @res << " #{attr}='#{value}'"}if block_given?

@res << ">"inside = yield@res << inside.to_s@res << "</#{name}>"

else@res << ' />'

endnil

end

DSL RPG Иху‐аху

Game.new dopencho = Singlerich.new('Pencho')kuncho = Eigendiel.new('Kuncho')

kuncho.knife penchokuncho.bow penchokuncho.sword kuncho

pencho.kick kunchoputs kuncho.health pencho.healthend

class Eigendiel < Monster

weapons :bow, :knife

def after_bow(other)# special poison, doesn’t work on meother.hurt 2 if !other.equal?(self)

endend

class Singlerich < Monster

weapons :knife, :sword, :kick

def before_knife(other)# kicks at the same timekick other

endend

class Monsterattr_reader :health, :name

BASIC_DAMAGE = 11

def initialize(name)@name = name@health = 100

end

def self.weapons(*weapons_list)

?end

def hurt(amount)@health ‐= amountputs "#{@name} is a loser!\n" if @health < 0

end

end

def self.weapons(*weapons_list)weapons_list.each do |weapon|weapon = weapon.to_sdefine_method weapon do |whom|

send "before_#{weapon}", whom if self.class.method_def...whom.hurt BASIC_DAMAGEsend "after_#{weapon}", whom if self.class.method_def...

endend

end

Game.new dopencho = Singlerich.new('Pencho')kuncho = Eigendiel.new('Kuncho')

kuncho.knife penchokuncho.bow penchokuncho.bow kuncho

chuck = Singlerich.new("Chuck")def chuck.explode(whom)

whom.hurt 100end

chuck.explode penchochuck.explode kuncho

end

4. Метапрограмиране

Technology

end end end end end

false vector

length true vector

true rubyist vector

variables quot

class vector attr

class rubyist chunky

end endpesho