From: Doug Jolley <lists@...>
Date: 2012-07-01T07:37:15+09:00
Subject: Re: Accessor Methods with a Twist

Thanks, Jan, so much for that *VERY* thorough response.

> I seems you haven't fully understood the concept of object orientation.

I'm sure that's an understatement.  However, I am wrestling with it. :-)

I was aware of many of the things that you mentioned in your response.
I think that my real issue turns on this statement in your response:

> Of course, you can do this not only on the top level but also in modules
> or anywhere else. But you have to create an instance of Person first.

My understanding was that when I did:

> person_1 = Person.new 'Doug'

the left-hand-side was a local variable.  After reading your response, I
thought that maybe it isn't.  Maybe it's something else that would be
available in a module.  I used the following code (which draws heavily
on your example) to test this hypothesis:

class Person

  def initialize name
    @name = name
  end

  def name()
    @name
  end

  def name=(new_name)
    @name = new_name
  end

end

person_1 = Person.new 'Doug'

module MyModule
  def self.show_name()
    puts(person_1.name())
  end
end

MyModule.show_name()

=> ./test2:23:in `show_name': undefined local variable or method
`person_1' for MyModule:Module (NameError)

So, I'm not exactly sure what you mean when you say:

> Of course, you can do this not only on the top level but also in modules
> or anywhere else.

I cannot seem to access the accessor methods from within a module.
That's what I'd like to be able to do.

Thanks ever so much for hanging in there with me.  I think I'm on the
verge of a major breakthrough in understanding.  Thanks again.

> Some other things to note:
> - You don't have to write getters and setters by hand. You can simply
> call "attr_accessor" within the class body and supply the variable names
> as Symbols:

Understood.

> - You don't have to use parantheses for method calls. While many people
> still use them for clarity, it's common to omit them for basic methods
> like "puts" and getter methods (this makes it look like you were
> actually accessing the variables of the object rather than calling
> methods).

I understand that and within the context of simple things like puts, I
agree.  It's just that I am trying to force myself to remember to use
parenthesis with methods so that when I go to review the code it's more
clear which identifiers are variables and which are methods.

> - I wouldn't use "::" when calling module or class methods. This is
> allowed, but I'd rather stick with the normal dot and use the double
> colon only for constants.

That's a revelation.  Thanks.

> - When define class methods inside a class body, you should use "self"
> as the receiver rather than write out the actual class name. This makes
> the code much more flexible, because renaming the class won't break the
> whole code.

Good point.  I'll try to remember that.

      ... doug

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