metaprogramming.rb

class Car
  def initialize(options)
    @color = options[:color]; @make = options[:make]; @model = options[:model]
  end
  
  def color; @color; end
  
  def make; @make; end
    
  def model; @model; end
  
  def color=(new_color); @color = new_color; end
  
  def make=(new_make); @make = new_make; end
  
  def model=(new_model); @model = new_model; end
end

$ irb
1.9.3-p125 :001 > class Car
1.9.3-p125 :002?>     def initialize(options)
1.9.3-p125 :003?>         @color = options[:color]; @make = options[:make]; @model = options[:model]
1.9.3-p125 :004?>       end
1.9.3-p125 :005?>
1.9.3-p125 :006 >       def color; @color; end
1.9.3-p125 :007?>
1.9.3-p125 :008 >       def make; @make; end
1.9.3-p125 :009?>
1.9.3-p125 :010 >       def model; @model; end
1.9.3-p125 :011?>
1.9.3-p125 :012 >       def color=(new_color); @color = new_color; end
1.9.3-p125 :013?>
1.9.3-p125 :014 >       def make=(new_make); @make = new_make; end
1.9.3-p125 :015?>
1.9.3-p125 :016 >       def model=(new_model); @model = new_model; end
1.9.3-p125 :017?>   end
 => nil
1.9.3-p125 :018 > Car.new(:color => "blue", :make => "ford", :model => "mustang")
 => #<Car:0x007fc6ea06df98 @color="blue", @make="ford", @model="mustang">
1.9.3-p125 :019 > c = Car.new(:color => "blue", :make => "ford", :model => "mustang")
 => #<Car:0x007fc6ea8ded80 @color="blue", @make="ford", @model="mustang">
1.9.3-p125 :020 > c.color
 => "blue"
1.9.3-p125 :021 > c.make
 => "ford"
1.9.3-p125 :022 > c.model
 => "mustang"
1.9.3-p125 :023 > c.color = "red"
 => "red"
1.9.3-p125 :024 > c.color
 => "red"


class Car
  def initialize(options)
    @color = options[:color]; @make = options[:make]; @model = options[:model]
  end
  
  ["color", "make", "model"].each do |property|
    eval "def #{property}; @#{property}; end"
    eval "def #{property}=(new_#{property}); @#{property} = new_#{property}; end"
  end
end


1.9.3-p125 :001 > class Car
1.9.3-p125 :002?>     def initialize(options)
1.9.3-p125 :003?>         @color = options[:color]; @make = options[:make]; @model = options[:model]
1.9.3-p125 :004?>       end
1.9.3-p125 :005?>
1.9.3-p125 :006 >       ["color", "make", "model"].each do |property|
1.9.3-p125 :007 >           eval "def #{property}; @#{property}; end"
1.9.3-p125 :008?>         eval "def #{property}=(new_#{property}); @#{property} = new_#{property}; end"
1.9.3-p125 :009?>       end
1.9.3-p125 :010?>   end
 => ["color", "make", "model"]
1.9.3-p125 :011 > c = Car.new(:color => "blue", :make => "ford", :model => "mustang")
 => #<Car:0x007f94bb8ade80 @color="blue", @make="ford", @model="mustang">
1.9.3-p125 :012 > c.color
 => "blue"
1.9.3-p125 :013 > c.make
 => "ford"
1.9.3-p125 :014 > c.model
 => "mustang"
1.9.3-p125 :015 > c.color = "red"
 => "red"
1.9.3-p125 :016 > c.color
 => "red"