On 28 août, 09:46, Ricardo Rocha <[email protected]> wrote:
> Hi Etienne.
>
> On Aug 28, 1:00 am, Etienne Neveu <[email protected]> wrote:
>
> > Hi Ricardo and Thomas,
>
> > I don't know much about UIBinder (excepted that it seems promising and
> > that I'll have to look into it!), but I might have an idea regarding
> > the use of GIN / DI to improve upon Thomas' suggestion of:
> > "revers[ing] the dependency and hav[ing] StatsView instantiate its
> > StatsPresenter and keep a reference to it in a private field".
>
> > I got this idea the other day while reading this semi-related google-
> > guice thread
> > :http://groups.google.com/group/google-guice/browse_thread/thread/2509...
> > .
>
> > What about:
>
> > - adding a provider method in your GinModule:
>
> > @Provides
> > StatView provideStatView(StatPresenter statPresenter) {
> > return statPresenter.getView();
>
> > }
>
> > - then injecting the view where you need it:
> > public MainView extends View {
>
> > private final StatView statView;
>
> > @Inject
> > public MainView(StatView statView) {
> > this.statView = statView;
> > }
>
> > }
>
> > When Gin creates the MainView, it looks a StatView to inject, sees
> > that it is provided by the @Provides method, creates and injects
> > dependencies into a new presenter (including a new view associated to
> > this presenter), and then returns the view.
> > You can then inject multiple StatViews in your UI, and they will each
> > create their associated presenter.
>
> > If you want a singleton StatView, make the StatPresenter a singleton.
> > In this case, the @Provides method will create the presenter the first
> > time it is called, but will re-use this presenter (and associated
> > view) the following times.
> > You wouldn't even need to declare the StatView as a Singleton, because
> > its scope would be the same as the StatPresenter's scope, due to the
> > use of the @Provides method.
>
> > In this case, your view would not have to instantiate your presenter /
> > keep a reference to it. Gin does the magic for you. Which is IMO good
> > for the separation of concerns.
>
> > What do you think?
>
> I gave this a try, it looks nice. But couldn't make it work, here's
> what i did.
>
> In my injector module:
>
> @Provides
> StatsView getStatsView(StatsPresenter presenter) {
> return (StatsView)presenter.getDisplay();
> }
>
> In my StatsPresenter constructor:
>
> @Inject
> public StatsPresenter(final Display display, EventBus eventBus,
> final DispatchAsync dispatch) {
>
> It looks ok, but the Display in the StatsPresenter is a StatsView
> instance, so i additionally have in my injector module:
>
> bind(StatsPresenter.Display.class).to(StatsView.class);
>
> I get a StackOverflowError, which i'm thinking is due to a loop in the
> DI. Instantiating a StatsPresenter will trigger the need for a
> StatsPresenter.Display which is a StatsView, which then instantiates a
> StatsPresenter, ... just a guess but it looks like this.
Yes, typical circular dependencies...
You can simply use a named binding for where you want your StatsView
to be injected (not tested!):
// will inject a StatsView instance into StatsPresenter
bind(StatsPresenter.Display.class).to(StatsView.class);
...
@Provides @Named("er...no idea")
public StatsView providesStatsViewFromStatsPresenter(StatsPresenter
presenter) {
return presenter.getView();
}
and in your MainPresenter:
@Inject
MainView(@Named("er...no idea") StatsView statsView) {
...
But all of this also depends on how you're typically injecting your
presenter+view into other presenter+view (where the presenter has some
public methods that the "parent" presenter will call); then even if
StatsPresenter has no such method, I would inject it the same, just
for the sake of being consistent throughout the app.
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