Why don't you simply pass the class and use that class in your MovieLister?
MovieLister new
finderClass: MySuperCoolFinderClass
...
MovieLister finder
finderClass new .....
What is wrong with that.
If you do not want to have a reference at runtime to a Finder then you
need to use announcement and registration.
Stef
On Sun, Jun 4, 2017 at 11:17 PM, Vitor Medina Cruz <vitormc...@gmail.com> wrote:
> Hello,
>
> I would like to know how people in Pharo ecosystem do to deal with object
> wiring, as described by Marting Fowler in
> https://martinfowler.com/articles/injection.html#FormsOfDependencyInjection:
>
> "A common issue to deal with is how to wire together different elements: how
> do you fit together this web controller architecture with that database
> interface backing when they were built by different teams with little
> knowledge of each other."
>
> He gives an example, I will leave it in java as it is simple enough to
> understand:
>
> "class MovieLister...
>
> public Movie[] moviesDirectedBy(String arg) {
> List allMovies = finder.findAll();
> for (Iterator it = allMovies.iterator(); it.hasNext();) {
> Movie movie = (Movie) it.next();
> if (!movie.getDirector().equals(arg)) it.remove();
> }
> return (Movie[]) allMovies.toArray(new Movie[allMovies.size()]);
>
> }"
>
> The question is how to provide the finder object in a decoupled matter, a
> naive approach would be:
>
> " private MovieFinder finder;
>
> public MovieLister() {
> finder = new ColonDelimitedMovieFinder("movies1.txt");
>
> }"
>
> Which couples the MovieLister to the specific ColonDelimitedMovieFinder
> class.
>
> Fowler explains how to decouple using an IoC framework or a Service Locator.
> In Java and .Net IoC is used most of the time. I Googled how this problem is
> approached in Smalltalk/Pharo, and I generally I found answers "that is easy
> to do in Smalltalk, so there is no need of a framework", what I miss is a
> description on *how* to do that:
>
> https://stackoverflow.com/questions/243905/smalltalk-and-ioc
> https://stackoverflow.com/questions/2684326/is-there-a-dependency-injection-framework-for-smalltalk
> https://stackoverflow.com/questions/243905/smalltalk-and-ioc/347477#347477
>
> I know that in Smalltalk I can make MovieLister to receive, upon
> construction, a class representing MovieFinder and call it construction
> message. As long an object that responds to this message is provided, I can
> create as many derivations I want and the MovieLister will be decoupled from
> the MovieFinder. That way, however, I still have to wire things by hand, and
> I am not sure if this is what I am supposed to do in order to solve the
> decouple problem.
>
> Can you explain me how this is done in Pharo? It's is usually wiring by
> hand? Is there a simple construction that deals with the wiring problem that
> I cannot foresee?
>
> Thanks in advance,
> Vitor
>
>
>
