module 中的 public method 对于被 include 所在的 class 来说是 instance method,故 object.public_method_in_module 能调用。如果想要非 module method 能够被 module 调用(module_name.not_module_method) ,需要引入 extend self (下文会讨论 extend self)
# test.rb
module MyModule
def public_meth
p "a public method, if the module is included to a class , can be call as object.public_meth"
end
def module_method
p "a module method,can be called as module_name.module_method. but can not be call as object.module_method"
end
private
def private_method_to_module_function
p "a private_method, but can be call as module_name.module_method, because it was assigned to module_function"
end
def private_method
p "I am a private method"
end
module_function :module_method, :private_method_to_module_function
end
MyModule.module_method
MyModule.private_method_to_module_function
begin
MyModule.public_meth
rescue
p "public method can not be called by module_name.public_meth"
end
begin
MyModule.private_method
rescue NoMethodError
p "private method can not be called by module_name.module_method"
end
class MyClass
include MyModule
end
obj = MyClass.new
obj.public_meth
begin
obj.private_method
rescue NoMethodError
p "private method in module can not be call by object.method_name"
end
begin
obj.module_method
rescue NoMethodError
p "module method can not be called by object.method_name, for object, module method is private instance method"
end
#调用
ruby test.rb
"a module method,can be called as module_name.module_method. but can not be call as object.module_method"
"a private_method, but can be call as module_name.module_method, because it was assigned to module_function"
"public method can not be called by module_name.public_meth"
"private method can not be called by module_name.module_method"
"a public method, if the module is included to a class , can be call as object.public_meth"
"private method in module can not be call by object.method_name"
"module method can not be called by object.method_name, for object, module method is private instance method"
总结就是
•The method will be copied to class' singleton class
•The instance method's visibility will become private extend self
Include is for adding methods to an instance of a class and extend is for adding class methods
extend 本质是给 class 或者 module 添加 class method
#!/usr/bin/env ruby
# encoding: utf-8
# test_extend.rb
module MyModule
extend self
def public_meth
p "a public_method extended by self can be called by module_name.public_meth and object.public_meth, included by a class"
private_method
end
private
def private_method
p "a private method, can be call in module internal"
end
end
class MyClass
include MyModule
end
MyModule.public_meth
begin
MyModule.private_method
rescue NoMethodError
p "private method in extend self module can not be called module_name.private_method"
end
obj = MyClass.new
obj.public_meth
begin
obj.private_method
rescue NoMethodError
p "private method can not be called by object.private_method"
end
# 调用 ruby test_extend.rb
"a public_method extended by self can be called by module_name.public_meth and object.public_meth, included by a class"
"a private method, can be call in module internal"
"private method in extend self module can not be called module_name.private_method"
"a public_method extended by self can be called by module_name.public_meth and object.public_meth, included by a class"
"a private method, can be call in module internal"
"private method can not be called by object.private_method"