metaprogramming

struct.rb

#Struct allows you to define classes that contain just data attributes.
Person = Struct.new(:name, :address, :likes)

dave = Person.new('Dave', 'TX')
dave.likes = "Programming Languages"
puts dave

# opening up the class and writing the method
Person = Struct.new(:name, :address, :likes)
class Person
  def to_s
    "#{self.name} lives in #{self.address} and likes #{self.likes}"
  end
end

# < 的右侧可以是个class名称,也可以是返回class对象的表达式。
class Person < Struct.new(:name, :address, :likes)
  def to_s
    "#{self.name} lives in #{self.address} and likes #{self.likes}"
  end
end

dave = Person.new('Dave', 'Texas')
dave.likes = "Programming Languages"
puts dave