(Ruby,Rails) Context of SELF in modules and librar

问题:

Quick question regarding the use of "SELF" inside a module or library. Basically what is the scope/context of "SELF" as it pertains to a module or library and how is it to be properly used? For an example of what I'm talking about, check out the "AuthenticatedSystem" module installed with "restful_authentication".

NOTE: I'm aware that 'self' equates to 'this' in other languages and how 'self' operates on a class/object, however in the context of a module/library there is nothing to 'self'. So then what is the context of self inside something like a module where there is no class?

回答1:

In a module:

When you see self in an instance method, it refers to the instance of the class in which the module is included.

When you see self outside of an instance method, it refers to the module.

module Foo
  def a
    puts "a: I am a #{self.class.name}"
  end

  def Foo.b
    puts "b: I am a #{self.class.name}"
  end

  def self.c
    puts "c: I am a #{self.class.name}"
  end
end

class Bar
  include Foo

  def try_it
    a
    Foo.b # Bar.b undefined
    Foo.c # Bar.c undefined
  end
end

Bar.new.try_it
#>> a: I am a Bar
#>> b: I am a Module
#>> c: I am a Module

回答2:

For a short summary... http://paulbarry.com/articles/2008/04/17/the-rules-of-ruby-self

self is also used to add class methods (or static methods for C#/Java people). The following snippet is adding a method called do_something to the current class object (static)...

class MyClass
    def self.do_something   # class method
       # something
    end
    def do_something_else   # instance method
    end
end