Singleton method
is method is defined for only one instance
class Foo
def bar
:bar
end
end
foo = Foo.new
p foo.bar #=> bar
def foo.baz
:baz
end
p foo.baz #=> baz
Singleton class
is class have only one instance
require "singleton"
class Foo
include Singleton
end
foo, foo1 = Foo.instance, Foo.instance
foo == foo1 #=> true
Foo.new #=> Runtime Error