From: Christian Neukirchen <chneukirchen@...>
Date: 2006-04-30T18:18:06+09:00
Subject: Re: [ANN] MinDI 0.3

Joel VanderWerf <vjoel@path.berkeley.edu> writes:

> <i>Using the InjectableContainer module for "dynamic" or "fallback"
> injection, using <tt>method_missing</tt>:</i>
>
>   require 'mindi'
>
>   class Transformer
>     def transform string
>       string.gsub(pattern, &replacement)
>     end
>   end
>
>   class TransformerContainer
>     include MinDI::InjectableContainer
>
>     pattern     { /foo/ }
>     replacement { proc {|match| match.upcase } }
>     transformer { Transformer.new }
>     transform   { |str| transformer.transform(str) }
>   end
>
>   cont = TransformerContainer.new
>   s1 = cont.transform("fo foo fee")
>   s2 = cont.transform("fo foo fee")
>   p s1              # ==> "fo FOO fee"
>   p s1.equal?(s2)   # ==> true
>
>
> Note that the Transformer class is written without explicitly linking up
> to services (either in initialize or in setters). It just assumes that
> the services will be defined in the container.

So, if I get that right... the Transformer instance gets extended with
the TransformerContainer automatically?  Or how does it know about
"pattern" and "replacement"?

Isn't that a clear and obvious violation of encapsulation?
And won't it hide lots of bugs due to typos or doubly defined methods?

> Note also that the #transform service is a multiton service, and (like
> singleton services) it caches its value for each argument.
>
> -- 
>       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
>

-- 
Christian Neukirchen  <chneukirchen@gmail.com>  http://chneukirchen.org