Dress Up 
Let's play dress-up! Dress Up allows you to specify named sets of method overrides that you can selectively enable and disable. It makes for a sort of an on-the-fly decorator pattern.
Compatibility
Dress Up relies on the Ruby 1.9.X ordering of Hash entries.
Example
Below is the Duck class that has defined two costumes: dog and robosoldier. The dog costume overrides the name= method to append "Dog" and the speak method to return "Woof!". The robosoldier costume overrides speak as well and adds a new method, terminations.
class Duck
# include the Dress Up functionality
include DressUp
attr_accessor :name, :age
# define a dog costume
costume :dog, :name= => lambda {|name| @name = name + " Dog"}, :speak => "Woof!"
# define a robosoldier costume
costume :robosoldier, :speak => lambda {"I will terminate you! " + super()}, :terminations => 23
def initialize(name, age)
@name, @age = name, age
end
def speak
"Quack!"
end
end
When the dog costume is applied, it overrides the methods it specifies:
duck = Duck.new("Horace", 2)
duck.put_on(:dog)
duck.name = "George"
puts duck.name
=> "George Dog"
puts duck.speak
=> "Woof!"
When the robosoldier costume is applied, its overrides are merged with dog's overrides and reapplied.
duck.put_on(:robosoldier)
puts duck.speak
=> "I will terminate you! Quack!"
puts duck.terminations
=> 23
When the dog and robosoldier costumes are removed, their overrides are removed.
duck.take_off(:dog)
duck.name = "T1000"
puts duck.name
=> "T1000"
duck.take_off(:robosoldier)
puts duck.speak
=> "Quack!"
puts duck.terminations
=> NoMethodError
All the costumes can be applied at once:
duck.dress_up
duck.name = "Bob"
puts duck.name
=> "Bob Dog"
puts duck.terminations
=> 23
They can also all be removed at once:
duck.dress_down
puts duck.speak
=> "Quack!"
Access all of Duck's costumes:
Duck.closet
=> {:dog => <DressUp::Costume ... >, ...}
Access a duck's current outfit:
duck.put_on(:dog)
duck.outfit
=> <DressUp::Outfit ... >
Future Considerations
- Instead of merging overrides, just define overrides in sequence