wrote:
> > \> Anyone else got views on this??
> >
> > It looks like Ruby 1.9 will give you the ability to define private
> > methods in the base class (which may be simple getter/setter methods)
> > that are accessible to the base class, but not the descendents. Of
> > course the subclass will still have access to the instance variables -
> > in my opinion it would be madness to have 'inheritance' without this.
---
### Author:  [@Gary\_Wright](https://rubytalk.org/u/Gary_Wright)
#### Post date: [29 January 2007 01:34 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/12 "2007-01-29T01:34:16Z")
Bertrand Meyer in Object Oriented Software Engineering talks a lot
about the differences between the client and subclass relationships.
If I recall, he argues that a choice to subclass is in effect a choice
to reuse implementation.
Delegation is another way to reuse a class without gaining access to
private information.
Gary Wright
> **路路路**
>
> On Jan 27, 2007, at 7:10 PM, Richard Roberts wrote:
>
> > Anyway, looks like it's just the way it is in ruby, and I'm going to
> > have to be careful when I inherit.
---
### Author:  [@Richard\_Roberts](https://rubytalk.org/u/Richard_Roberts)
#### Post date: [27 January 2007 19:50 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/13 "2007-01-27T19:50:52Z")
I'm glad not everyone thinks I'm mad!
Does anyone know a good way to simulate the C++ and Java behaviour in
ruby? I've tried various things, but to no avail (e.g. declaring them as
class-level instance variables in a private block, creating private
accessors etc).
Avdi Grimm wrote:
"\> To the contrary, it's not madness at all"
> **路路路**
>
> --
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).
---
### Author:  [@Wolfgang\_Nadasi-Don1](https://rubytalk.org/u/Wolfgang_Nadasi-Don1)
#### Post date: [27 January 2007 20:40 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/14 "2007-01-27T20:40:09Z")
Avdi Grimm schrieb:
> To the contrary, it's not madness at all. It's a legitimate
> interpretation of OO principles to say that a private member variable
> is private to a class, and should be inaccessible to all clients of
> the class - INCLUDING derived classes.
I think this not possible in Ruby in general, because onybody can change a class later.
It's normal practice to write code in Ruby, which changes classes of the standard library.
\>\>\>\>\> Example \>\>\>\>\>
class Otto
def show
puts "here is 'show'"
end
private
def hiddenshow
puts "here is 'hiddenshow'"
end
end
o = Otto.new
o.show
o.hiddenshow rescue puts '+++ cannot call hiddenshow'
class Otto
public :hiddenshow
end
o.hiddenshow
\>\>\>\>\> Output \>\>\>\>\>
here is 'show'
+++ cannot call hiddenshow
here is 'hiddenshow'
\>\>\>\>\> EoE \>\>\>\>\>
Wolfgang N谩dasi-Donner
---
### Author:  [@Vincent\_Fourmond](https://rubytalk.org/u/Vincent_Fourmond)
#### Post date: [27 January 2007 20:11 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/15 "2007-01-27T20:11:21Z")
Richard Roberts wrote:
> I'm glad not everyone thinks I'm mad!
>
> Does anyone know a good way to simulate the C++ and Java behaviour in
> ruby? I've tried various things, but to no avail (e.g. declaring them as
> class-level instance variables in a private block, creating private
> accessors etc).
Write a C structure holding your variables (it doesn't even have to be
complex: a VALUE array should do). Apart from that, no solution. You
won't change easily a design feature of Ruby ;-)...
Vince
> **路路路**
>
> --
> Vincent Fourmond, PhD student (not for long anymore)
> [http://vincent.fourmond.neuf.fr/](http://vincent.fourmond.neuf.fr/)
---
### Author:  [@7rans](https://rubytalk.org/u/7rans)
#### Post date: [28 January 2007 01:29 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/16 "2007-01-28T01:29:24Z")
Use define\_method against local vars.
class X
x = 100
define\_method(:x) do ; x; end
end
X.new.x #=\> 10
Generalizing this, perhaps make use an OpenStruct (or Facets'
OpenObject class) and use that for local vars:
class X
local = OpenObject.new
local.x = 10
define\_method(:x) do
local.x
end
end
Personally I think Ruby would do well to make it's method defintion
syntax uniform across def and define\_method. Instead it could control
scope via alternate forms of 'do'. In other words, let 'def' be a
method too, or at least a short hand that actually calls
define\_method. It would be nice to write:
class X
local = OpenObject.new
local.x = 10
def x does
local.x
end
end
Where 'does' keeps the scope open.
T.
> **路路路**
>
> On Jan 27, 2:50 pm, Richard Roberts \ wrote:
>
> > I'm glad not everyone thinks I'm mad!
> >
> > Does anyone know a good way to simulate the C++ and Java behaviour in
> > ruby? I've tried various things, but to no avail (e.g. declaring them as
> > class-level instance variables in a private block, creating private
> > accessors etc).
---
### Author:  [@Avdi\_Grimm1](https://rubytalk.org/u/Avdi_Grimm1)
#### Post date: [28 January 2007 21:07 UTC](https://rubytalk.org/t/instance-variables-available-in-derived-clases/34858/17 "2007-01-28T21:07:22Z")
Whoa! That's cool!
I love how no matter how long I program in Ruby, I still get pleasant
surprised like this.
Thanks!
> **路路路**
>
> On 1/27/07, Trans \ wrote:
>
> > Use define\_method against local vars.
> >
> > class X
> > x = 100
> >
> > define\_method(:x) do ; x; end
> > end
> >
> > X.new.x #=\> 10
>
> --
> Avdi