Ruby supports two forms of objectified methods. Class Method is used to represent
methods that are associated with a particular object: these method objects
are bound to that object. Bound method objects for an object can be created
using Object#method.
Ruby also supports unbound methods; methods objects that are not associated
with a particular object. These can be created either by calling
Module#instance_method or by calling unbind on a
bound method object. The result of both of these is an
UnboundMethod object.
Unbound methods can only be called after they are bound to an object. That object must be be a kind_of? the method's original class.
class Square
def area
@side * @side
end
def initialize(side)
@side = side
end
end
area_un = Square.instance_method(:area)
s = Square.new(12)
area = area_un.bind(s)
area.call #=> 144
Unbound methods are a reference to the method at the time it was objectified: subsequent changes to the underlying class will not affect the unbound method.
class Test
def test
:original
end
end
um = Test.instance_method(:test)
class Test
def test
:modified
end
end
t = Test.new
t.test #=> :modified
um.bind(t).call #=> :original