Design Patterns discussion

["Santana, Luis" <luis.santana AT eds.com>]

I agree with Eduardo, without knowing much about the context, the best
suitable pattern would be "Abstract Factory"... The 'family' of your product
is "CParaAccess" and your "concrete" products would be "CFileParaAccess" and
"CDatabaseParaAccess". 

Regards, 

Luis Santana

-----Original Message-----
From: Zhai 
[mailto:myzhai AT yahoo.com.cn]
 
Sent: Wednesday, March 03, 2004 8:24 AM
To: Eduardo Franco; 
gang-of-4-patterns AT cs.uiuc.edu
Subject: Re: [gang-of-4-patterns] discuss the usage of Strategy DP


At first, I try to use Abstract Factory to design the
system. According to the intend of Abstract Factory,
it can produce a family of products. But in our
system, we do not know what the family of products is.
So we next consider to use Strategy design pattern.
we need more advice. 

--- Eduardo Franco 
<eduardo.franco AT pulso.com.br>
的正文：> I don't think the Strategy is the best
pattern for
> your problem. I don't
> even know much about the context your are developing
> the system, but
> AFAICS the best suitable pattern is the "Abstract
> Factory".
> 
> [..]
> 
> "Provide an interface for creating families of
> related or dependent
> objects without specifying their concrete classes."
> 
> [..]
> 
> This pattern let you vary families of product
> objects when the
> "Strategy" pattern let you vary an algorithm which I
> don't think is your
> real problem.
> 
> Regards,
> 
> --
> Eduardo Franco
> 
> Zhai wrote:
> > In a software system, we meet the following
> > requirements:
> >   a client program, when running, have to set or
> get a
> > parameter, named paraValue.
> > But the parameter paraValue could be stored in a
> file
> > named filePara, or in a relation
> > database, such as Oracle. Now we design an
> abstract
> > class "CParaAccess", with two
> > public virtual functions setPara() and getPara()
> to
> > set and get the parameter.
> > There are two subclasses "CFileParaAccess" and "CDatabaseParaAccess" 
> > inherited  from "CParaAccess", all implement setPara() and
> > getPara(). However in 
> >  "CFileParaAccess" and "CDatabaseParaAccess", the
> > principle to implement
> >  setPara() and getPara() is different. 
> >    In the design we can understand the client had
> two
> > strategies to set/get the
> >  parameter, i.e. from a file or a database. so can
> we
> > think our design cohere
> >  with the Strategy design pattern? If not, which
> > pattern could we use to improve
> >  the design?
> >  thx.
> 
> 
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