From: John Feminella <johnf@...>
Date: 2011-02-23T21:55:37+09:00
Subject: Re: Calling class method from instance method

First, write your class method so that it accepts an instance:

==== begin snippet ====
class ExtendedFile
  attr_accessor :filename

  def self.process(file)
    if file.exists?
      # do some work
    end
  end

  def exists?
    self.exists? self.filename
  end
end
==== end snippet ====

Of course, once you can do that, then you can refactor the class
method into an instance method. Delete the method's argument and
replace it with a reference to `self`:

==== begin snippet ====
class ExtendedFile
  attr_accessor :filename

  def process # now it's an instance method
    if self.exists? # reference self instead of the argument
      # do some work
    end
  end

  def exists?
    self.exists? self.filename
  end
end
==== end snippet ====

~ jf
--
John Feminella
Principal Consultant, BitsBuilder
LI: http://www.linkedin.com/in/johnxf
SO: http://stackoverflow.com/users/75170/



On Wed, Feb 23, 2011 at 07:40, marco antonio f. <marcofognog@gmail.com> wrote:
> Ryan Davis ,
> "When you want to have a class call an "instance method", which instance
> would call it?"
>
> Good point! Makes sense.
>
> Anurag Priyam, this is pretty wierd... but works.
>
> You see, there's stuff that need to be donne in both cases, in instances
> and in classes. For example:
>
> class SomeClass
>  def self.method
>    if file_exists?
>      #do stuff
>    end
>    #something need to be donne here, and I need to check if the file
> exists
>    #I dont want to define a nother class method exactly the same as the
> already declared instance method.
>  end
>
>  def file_exists?
>    #there are instance methods depending on this one
>    File.exists?("some_file_name.txt")
>  end
> end
>
> How do you deal with this kind of thing?
>
> --
> Posted via http://www.ruby-forum.com/.
>
>