Sam,
Thanks for your response. It arrived when I was on vacation, so I
apologize for this late reply.
The approach I've taken is to just write out the Factory boilerplate:
class BarFactoryImpl implements BarFactory {
public <T> Bar<T> create(Foo<T> f) {
return new BarImpl<T>(f);
}
}
which then works with the simple binding
bind(BarFactory.class).to(BarFactoryImpl.class);
Regards,
Chris
On Oct 4, 8:54 am, Sam Berlin <[email protected]> wrote:
> See issue 218 <http://code.google.com/p/google-guice/issues/detail?id=218>.
> An assisted inject factory itself can be genericized, but its methods cannot
> introduce their own generic types right now. So assuming you have a limited
> number of types T, you can workaround this by changing BarFactory to
> BarFactory<T> and registering a BarFactory for each T.
>
> sam
>
> On Mon, Sep 27, 2010 at 10:58 AM, Chris Conway <
>
>
>
>
>
>
>
> [email protected]> wrote:
> > The following code is an example of a factory that produces a `Bar<T>`
> > given a `Foo<T>`. The factory doesn't care what `T` is: for any type
> > `T`, it can make a `Bar<T>` from a `Foo<T>`.
>
> > import com.google.inject.*;
> > import com.google.inject.assistedinject.*;
>
> > class Foo<T> {
> > public void flip(T x) { System.out.println("flip: " + x); }
> > }
>
> > interface Bar<T> {
> > void flipflop(T x);
> > }
>
> > class BarImpl<T> implements Bar<T> {
> > Foo<T> foo;
>
> > �...@inject
> > BarImpl(Foo<T> foo) { this.foo = foo; }
>
> > public void flipflop(T x) { foo.flip(x);
> > System.out.println("flop: " + x); }
> > }
>
> > interface BarFactory {
> > <T> Bar<T> create(Foo<T> f);
> > }
>
> > class Module extends AbstractModule {
> > public void configure() {
> > bind(BarFactory.class)
> > .toProvider(
> > FactoryProvider.newFactory( BarFactory.class,
> > BarImpl.class )
> > );
> > }
> > }
>
> > public class GenericInject {
> > public static void main(String[] args) {
> > Injector injector = Guice.createInjector(new Module());
>
> > Foo<Integer> foo = new Foo<Integer>();
> > Bar<Integer> bar =
> > injector.getInstance(BarFactory.class).create(foo);
> > bar.flipflop(0);
> > }
> > }
>
> > When I run the code, I get the following errors from Guice:
>
> > 1) No implementation for BarFactory was bound.
> > at Module.configure(GenericInject.java:38)
>
> > 2) Bar<T> cannot be used as a key; It is not fully specified.
>
> > I guess the problem is that the BarFactory.create() method doesn't
> > match the pattern expected by FactoryProvider, because of the type
> > quantifier <T>. But there isn't a real problem here: BarImpl.class
> > (with no type literal) is exactly what we need to create a Bar<T>
> > given a Foo<T>. Is there a way to configure Guice to generate a
> > BarFactory instance for me, or do I just need to write the BarFactory
> > instance by hand?
>
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