Ruby Language Singleton Class Accessing Instance/Class Variables in Singleton Classes
Example
Singleton classes share their instance/class variables with their object.
class Example
@@foo = :example
end
def Example.foo
class_variable_get :@@foo
end
Example.foo #=> :example
class Example
def initialize
@foo = 1
end
def foo
@foo
end
end
e = Example.new
e.instance_eval <<-BLOCK
def self.increase_foo
@foo += 1
end
BLOCK
e.increase_foo
e.foo #=> 2
Blocks close around their instance/class variables target. Accessing instance or class variables using a block in class_eval or instance_eval isn't possible. Passing a string to class_eval or using class_variable_get works around the problem.
class Foo
@@foo = :foo
end
class Example
@@foo = :example
Foo.define_singleton_method :foo do
@@foo
end
end
Foo.foo #=> :example
