Re: Pattern for configuring child objects.

On Thu, 23 Feb 2012 11:27:18 +0000
Pedro Melo <[email protected]> wrote:

> Hi,
>=20
> On Thu, Feb 23, 2012 at 5:57 AM, Bill Moseley <[email protected]>
> wrote:
> > I often have classes that abstract out the work of fetching data
> > from multiple sources -- so I have attributes that hold instances
> > of the objects that do the actual work. =C2=A0 Each of these objects
> > need their own config.
> >
> > I've used three approaches to pass config to the contained objects,
> > but each seems a bit cumbersome. =C2=A0Just wondering if there's other
> > ideas.
>=20
> I've come across the same problem often times, and I never got a
> answer I was fully happy with.
>=20
> I've used two approaches in the past:
>=20
>  1. pass inner worker object fully created to the top level class: you
> create the worker object with whatever configuration you want, and
> then pass it in the top level constructor call;
>  2. use dependency injection or some variation of the concept: either
> have a singleton configuration manager and worker objects call into it
> for configuration information, or pass a CodeRef configuration
> callback to the top level object to be passed along to the worker
> objects, to be used in the same way.
>=20
> On the whole I rather like dependency injection because on my use
> cases I force the callers of the configuration manager to register
> themselves with it, and allow me to reconfigure live whenever the app
> receives a external event "there is new configuration available,
> please adjust yourselves". When this happens, the configuration
> manager can obtain the new configuration parameters, and signal all
> the registered clients that they should reconfigure at their
> convenience.
>=20
> Bye,


If you end up doing DI, take a look at using Bread::Board since it
makes such things pretty trivial.


--=20

Nicholas Perez
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http://search.cpan.org/~nperez/
http://github.com/nperez