From: Robert Klemme <shortcutter@...>
Date: 2010-04-16T20:16:55+09:00
Subject: Re: Is this good OOP structuring?

2010/4/16 Derek Cannon <novellterminator@gmail.com>:
> Robert, I think you were meaning to thank Josh!

Oh, yes of course.  Thanks for the correction!

> Anyway, thanks very much
> Josh for the great explanations. That answered all my questions! And
> Robert, your example really helped -- it was a great concrete example.

Good.

> I guess my only question now is: when is it appropriate to make methods
> static? In the example that was given earlier:
>
>>class CourseController
>>   def initialize(...) # whatever it needs
>>   end
>>
>>   def self.read_url(url)
>>     ...
>>     cc = new(...)
>>     ...
>>     cc
>>   end
>>
>>   def self.read_file(file_name)
>>   end
>>end
>
> I understand how one would use CourseController.read_url(xxx) and
> CourseController.read_file(xxx), but I don't understand why I'd need it.
>
> Without it being static, I could just make references to the instance
> variables, in this case, the url -- which would be passed through in the
> initialize constructor). That would eliminate the need for the parameter
> that both static methods carry, right?

No.  The static methods would just be convenience methods for frequent
ways to construct the CourseController.  Example

require 'open-uri'

class CourseController
  def initialize(courses_string)
    # parse string and create internal structure
  end

  def self.read_file(file_name)
    new(File.read(file_name))
  end

  def self.read_url(url)
    open(url) {|io| new(io.read)}
  end
end

You can even modularize it more by adding a method that will do the
parsing and output a complete initialized CourseController.
#initialize then might have an empty argument list or a different
list.  Of course I am speculating a bit here since I do not know your
application case's details.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/