From: 7stud -- <lists@...>
Date: 2012-11-27T02:49:07+09:00
Subject: Re: Novice: Understanding instance 'variables' and methods

Steve Tu wrote in post #1086523:
>
> So far, my understanding was that both methods and variables used lower
> case names,

That's true.

> and that methods could be written both with and without
> '()'.
>

That's correct.

> To me that then made the t.test line a bit confusing, as it
> appears to invoke the method test on t.
>

It does.

> How then could you ever access
> the instance variable test of t?
>

puts t.instance_variable_get(:@test)


Or, you can reopen the class and redefine test():

class Test
  def test
    @test
  end
end

result = t.test
puts result

--output:--
10

However, the example you posted is terrible, and no one would ever write 
code like that.

> Am I then also right in assuming that in Ruby there aren't any true
> visible instance variables,
>

Instance variables are "private" in ruby.  That means you cannot 
directly access an instance variable--instead you have to use a method 
to accesses an instance variable.

> as to make the variable visible, you have to
> include an accessor - which effectively creates the getter/setter of
> that variable?
>

You can either write an accessor by hand:

def test
  @test
end

Or, you can tell ruby to do it for you:

class Dog
   attr_reader :test

   def initialize(t)
     @test = t
   end
end

d = Dog.new(10)
puts d.test

--output:--
10



> So if I changed the above code to have an instance variable of 'value',
> with an accessor, I could then have:
>
>
> @test = @value = 10
>

No.  You could write something like:

class Dog
   attr_reader :test
   attr_accessor :value

   def initialize(t)
     @test = t
   end
end

d = Dog.new(10)
d.value = 'hello'  #setter
puts d.value    #getter



> BUT t.value is then really a
> call to the 'generated' getter of value - so is really a method call?
>

Yes.  In fact, when you write:

x = 1 + 2

"+" is actually the name of an Integer method.  And because "+" is the 
name of a method, you can write that line like this:

x = 1.+(2)
puts x

--output:--
3


> And in the above case, where a 'variable' and method have the same name,
> is there a way to force the use of a specific 'setter/getter' - ie to
> have t.test return the value of test, rather than call the method test
> on t?

Who cares?  You would never write a class that has two methods with the 
same name.

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