From: Sacha Schlegel <schlegel@...>
Date: 2003-05-16T11:59:15+09:00
Subject: Re: State Pattern Implementation

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Hi Robert and all

I am about to need a ruby state machine. Eg state handling code.

Did look at the state pattern in "Desing Patterns, E. Gamma, R. Helm, R.
Johnson, J. Vlissides, Addison-Weslay, 1995

Will try to do that with ruby.

Do YOU or anyone else have links to "implemented" ruby state pattern
code?

Concrete I have about 7 states and more transitions.

Did look at your solution. I think I would like to seperate the
different states with their own classes as they might get a little bit
bigger.

Sacha

On Tue, 2003-05-13 at 15:30, Robert Klemme wrote:
> Hi all,
>=20
> I'd like to hear what people think: is this a reasonable implementation o=
f
> the state pattern?  (Apart from the fact, that class Foo is quite useless=
.
> :-)  The other question is, whether rededinition of a method should issue
> a warning in verbose mode (suppressed here by Kernel#no_warn()).
>=20
> BOND$ cat state.rb
>=20
> module Kernel
>   def no_warn(&b)
>     old =3D $-w
>     begin
>       $-w =3D false
>       b.call
>     ensure
>       $-w =3D old
>     end
>   end
> end
>=20
> class Foo
>   def initialize
>     st1
>   end
>=20
>   def st1
>     no_warn do
>       def self.foo; 100; end
>       def self.bar; 101; end
>     end
>   end
>=20
>   def st2
>     no_warn do
>       def self.foo; 200; end
>       def self.bar; 201; end
>     end
>   end
> end
>=20
> f =3D Foo.new
>=20
> p f.foo
> p f.bar
>=20
> f.st1
> p f.foo
> p f.bar
>=20
> f.st2
> p f.foo
> p f.bar
> BOND$ ruby -w state.rb
> 100
> 101
> 100
> 101
> 200
> 201
> BOND$
>=20
>     robert
>=20
> <!DSPAM:3ec09f121074414349190912060420469>
--=20
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Sacha                                   Schlegel
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sacha@schlegel.li                www.schlegel.li
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