module_function
将给定的实例方法设为私有,然后复制并将它们作为公共方法放入模块的元类中。
extend self
将所有实例方法添加到模块的singleton中,使其可见性保持不变。
module M
extend self
def a; end
private
def b; end
end
module N
def c; end
private
def d; end
module_function :c, :d
end
class O
include M
include N
end
M.a
M.b # NoMethodError: private method `b' called for M:Module
N.c
N.d
O.new.a
O.new.b # NoMethodError: private method `b' called for O
O.new.c # NoMethodError: private method `c' called for O
O.new.d # NoMethodError: private method `d' called for O