From: Jamal Soueidan <jkhaledsoueidan@...>
Date: 2007-04-04T22:25:49+09:00
Subject: Re: Everything is a object?

James Gray wrote:
> On Apr 4, 2007, at 7:43 AM, Jamal Soueidan wrote:
> 
>>>> using it, but this has been misunderstood, you should somehow
>>> and so attempts to reference it will fail to produce a reference to
>>> an object. An attempt will also be made to apply the token to the
>>> current object as a method, and if this too fails then the
>>> interpreter has no choice but to flag an error condition because
>>> semantically your program is broken - it makes no sense.
>>
>> :D
>>
>> So until I assign something to it, the interpreter would know nothing
>> about what object it is.
> 
> I think it's probably better to say that until you assign it, it
> doesn't exist.  But yes, you are on the right track here.
> 
>> In C# you can declare every variable what type it is like this:
>> String mystring;
>>
>> I assume I could do that in Ruby also:
>> @var = String.new
>>
>> But no need since Ruby would take care of this automatic when you  
>> assign
>> something to variables.
> 
> C# cares what type a variable is.  It uses that information for
> things like method lookup.  Ruby does not.  A variable can hold
> whatever you like:
> 
> str = String.new
> # ...
> str = 5  # Ruby doesn't care that it's not a String now
> 
> This is called "dynamic typing" and is one of the great features of
> Ruby.  It does take some getting use to though, if you are joining us
> from a statically typed language.
> 
>> When I write attributes in my code:
>> attr_assoccer :var
>>
>> I assume > then < the interpreter knows only that @var is a object  
>> (base
>> class)?
>>
>> So before I can use @var.
> 
> Actually, the it doesn't exist until you define it rule only applies
> to local variables:
> 
> $ ruby -e 'p local_var'
> -e:1: undefined local variable or method `local_var' for main:Object
> (NameError)
> $ ruby -e 'p @inst_var'
> nil
> $ ruby -e 'p $global_var'
> nil
> 
> However, the last two issue warnings when enabled (which I recommend):
> 
> $ ruby -we 'p @inst_var'
> -e:1: warning: instance variable @inst_var not initialized
> nil
> $ ruby -we 'p $global_var'
> -e:1: warning: global variable `$global_var' not initialized
> nil
> 
> Hope that helps.
> 
> James Edward Gray II

Actually I was trying to do it this way, when I started.

if @var.nil?
  p "empty"
end

which works normal..but @var is nothing yet, and not declared, but still 
its object of object class?

Ruby understand that everything start with @ is a object, either 
reference or a type.

like in other language

@var = &reference
@var = object

when I type it

if var.nil?

var is unknown?

it's not variable, neither object? what is it? nobody knows, throw 
exception to the bad coder :P

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