Re: Pattern Question

Let me understand:

You are creating an abstraction whereby the actual type to be used in an
implementation is decided seperately from the use of the type. OK. Sounds
like very simple abstraction. Class Factory and simple inheritance.

Plug in and Registry both assume that the implementing object is compiled
seperately from the object that uses it, and that you use a bit of
redirection to find the proper implementation. However, it sounds like you
Don't want that... you want to decide at compile time, or at best, at run
time. That sounds like the Factory Method pattern.

It's almost too easy of an answer. I must be missing something. If I
misunderstood (quite likely), please provide more details. In a nutshell,
attempt to answer this design question: what is the reason you are adding
indirection in this case?

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--- Nick Malik [Microsoft]
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http://blogs.msdn.com/nickmalik

Disclaimer: Opinions expressed in this forum are my own, and not
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I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
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<russell@xxxxxxxxxxxxx> wrote in message
news:1164645191.427647.190820@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I am having a discussion with someone in my office about two patterns.


plug-in and registry.

What we are building is a global definition of what type to use in a
particular implementation. This makes it sound like a good match to
plug-in but here is my problem. The way we are doing it allows for the
particular implementations to inherit from each other. In fact core
product types can be replaced via this definition for a particular
implmentation.

My concern with plug-in is that it in the Patterns book I am using
(Martin Fowler's Patterns of Enterprise Application Architecture) talks
about a plug-in pattern as Linking types at configuration time not
compile time. What we are doing does not support the abstraction of
no compile time linking. Is that big enough to though it out of the
pattern?

Registry somewhat imples that you are accessing existing instances of
types. If we are mainly building new instances does that violate that
pattern too.

What you would call the application component defined above?



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