From: Nikolai Weibull <mailing-lists.ruby-talk@...>
Date: 2005-09-27T02:08:26+09:00
Subject: Re: [ANN] My dependency-injection library

Christian Neukirchen wrote:

> Nikolai Weibull <mailing-lists.ruby-talk@rawuncut.elitemail.org> writes:

> > OK.  So Ruby has enough dependency-injection/inversion-of-control
> > libraries as it is, but mine is quite different so I figured I’d
> > post it.  It’s about as simple as dependency-injection can possibly
> > become and there’s no support for lifecycles, interception, or other
> > framework stuff.  Nor is there any support for parents, children, or
> > other relatives, so keep it to yourself.

> Interesting idea, but you are only pushing constants around?

I’d like to think that we’re doing a bit more than that.

> Can't we do that easier?

Maybe.

> > class Scanner
> >   def initialize(io)
> >     raise Error, "can only work with open io-ports" if io.closed?
> >     @io = io
> >   end
> > end
> 
> > class Error < ScriptError; end # Or something more creative, perhaps?
>   Scanner::Error = Error
> 
> > class TC_Driver < Test::Unit::TestCase
> >   ⋮
> > end
> 
> > So the idea is that under normal circumstances, ‘needs’ is just a
> > circumvention for not using ‘require’ directly, but for trying times the
> > dependency can be changed to something more suitable.
> 
> I really fail to see the advantage of using this over manual require
> and dependency setting. :-)

Well, the thing is, what do you do when you have a compiler class

class Compiler
  ⋮
    raise Error, …
  ⋮
end

that also ‘needs’ our error class?

> I personally would expect a DI framework to at least provide a
> singleton instantiation scheme, else it wouldn't make any sense to me
> at all.

Well, maybe so, but the idea of my library is that all you really need
is to be able to bind constants to classes.  It’s definitely not much,
but I found that that was precisely what I was looking for.

> Einstein once said "Everything should be made as simple as possible,
> but not simpler".

Or something to that effect, yes.  (I have yet to find the actual source
of this quotation.  Not that I’m doubting that he said it, but I am
wondering if he said/wrote it in English or German and if there was some
context to it as well.)


> I think anything more simple than Matz-DI is too simple.
> > http://onestepback.org/articles/depinj/matz/index.html

Perhaps, but again, all I was looking for is done by my library.  I’m
certainly not trying to force people to stop using needle or some other
library (e.g., dissident).  To me, needle is doing a bit too much and I
seem to have a hard time reading your examples for dissident (how do you
do namespacing in dissident?), so I haven’t given it a chance yet,
        nikolai

-- 
Nikolai Weibull: now available free of charge at http://bitwi.se/!
Born in Chicago, IL USA; currently residing in Gothenburg, Sweden.
main(){printf(&linux["\021%six\012\0"],(linux)["have"]+"fun"-97);}