On Tue, Aug 10, 2010 at 11:01 AM, Peter Schmitt <[email protected]> wrote:
> I think the scheme I sketched gets around this issue. Gin isn't aware of
>> any of the generated code. Rather, the generated code is aware of the public
>> Ginjector interface. When Gin is asked to inject a MyUiBinder, it's just
>> going to write GWT.create(MyUiBinder), and then call that instance's
>> setFactory() method with itself. So this code:
>>
>> @Inject
>> public MyWidget(MyUiBinder binder) extends Composite {
>>
>> public interface MyUiBinder extends UiBinderWithFactory<Widget,
>> MyWidget,
>> MyGinjector> {
>> @Inject setFactory(MyGinjector factory);
>> }
>> }
>>
>>
>> makes Gin generate the moral equivalent of
>>
>> new
>> MyWidget((MyUiBinder.class) GWT.create(MyUiBinder.class)).setFactory(this);
>>
>>
> Yes, this should work. It requires some boilerplate on the ginjector (which
> often contains just a single method) but it has the advantage of not
> requiring any additional infrastructure.
>
>
>> Also, while I was assuming that for the most part the binder would be
>> working off of the Ye One True Ginjector, there is no actual requirement
>> that you do so, nor that your Factory be Ginjector at al. E.g.:
>>
>> @Inject
>> public MyWidget(MyUiBinder binder) extends Composite {
>>
>> public static class Factory {
>> @Inject @MagicScope EventBus eventBus;
>>
>> FooWidget makeAFoo() {
>> return new Foo(eventBus);
>> }
>> }
>>
>> public interface MyUiBinder extends UiBinderWithFactory<Widget,
>> MyWidget,
>> MyGinjector> {
>> @Inject setFactory(Factory factory);
>> }
>> }
>>
>>
> No problem - this factory is essentially a provider, although in the usual
> case it will have more than one creator method? You can also abuse assisted
> inject here to have Gin generate the implementation for the factory
> interface (assisted inject won't complain if you don't pass any local
> variables :).
>
Slick. I'll have to read up on that.
>
>
>> And if it's possible for one Ginjector to create another (haven't been
>> paying attention, sorry), that boilerplate could perhaps be even less?
>>
>> @Inject
>> public MyWidget(MyUiBinder binder) extends Composite {
>>
>> @MagicScope
>> public interface Factory extends Ginjector {
>> EventBus eventBus;
>> }
>>
>> public interface MyUiBinder extends UiBinderWithFactory<Widget,
>> MyWidget,
>> MyGinjector> {
>> @Inject setFactory(Factory factory);
>> }
>> }
>>
>>
> While this works in theory, you probably want a new ginjector that actually
> inherits the injection framework of the original ginjector - otherwise it
> won't have any of the bindings. Probably easier to use assisted inject as
> outlined above.
>
>
>> I think what we want is a class generated by UiBinder that has @Inject
>>> annotated constructor/fields/methods for its required children and is then
>>> used as input by the Gin generator to wire the injection up. But to
>>> accomplish that, we'll need to fix the issue mentioned above.
>>>
>>> How does this sound?
>>>
>>
>> Like it would need a lot more thought and a lot more work :-). (Although
>> it's a nicely DI-framework-agnostic notion, now that the annotations live in
>> javax.). We really wouldn't just want limit you to putting @Inject on
>> everything, you'd want the full gin experience — e.g. to be allowed to put
>> other annotations on specific fields, right? All of a sudden we have to
>> provide an annotation syntax for ui.xml.
>>
>> Don't get me wrong, I would rather fix GWT.create() so that Ginjector
>> actually could efficiently provide a getInstance(...) method, and to allow
>> gin to see generated code. But those two conversations never seem to
>> terminate, and I don't have the chops to just do them myself. So my question
>> is: if we accept the current limitations, would this change be a worthwhile
>> incremental step?
>>
>
> Yes, we should do the simple solution first. I'd really like to fix the
> generator interaction challenge though, it would solve tons of other
> problems as well.
>
I'll try to get this done, as I think it may solve a number of problems for
me, but no ETA.
Re: the correct solution, I don't think any of us can raise our hand. But I
bet we could get you pointed in the right direction if you want to roll up
your sleeves.
>
>
>
>>
>>> Peter
>>>
>>>
>>>
>>>
>>>> > public interface UiBinderWithFactory<U, O, F> extends UiBinder<U, O> {
>>>> > /**
>>>> > * Sets a factory to use when instantiating objects that are not
>>>> > * provided via @UiFactory methods or @UiField(provided = true)
>>>> fields.
>>>> > * <p>
>>>> > * When an instance is needed, a zero args method with an
>>>> appropriate
>>>> > return type
>>>> > * will be sought on the factory to provide it. If none is found
>>>> > GWT.create()
>>>> > * will be used instead.
>>>> > * <p>
>>>> > * It is a compile time error for the factory to provide ambiguous
>>>> > methods.
>>>> > */
>>>> > setFactory(F factory);
>>>> > }
>>>> >
>>>> > You might wind up with code like…
>>>> >
>>>> > @Inject
>>>> > public MyWidget(MyUiBinder binder) extends Composite {
>>>> >
>>>> > public interface MyUiBinder extends UiBinderWithFactory<Widget,
>>>> MyWidget,
>>>> > MyGinjector> {
>>>> > @Inject setFactory(MyGinjector factory);
>>>> > }
>>>> >
>>>> > …and a few extra getters on your Ginjector.
>>>> >
>>>> > Now injecting an injector is generally a terrible idea, but it's
>>>> something
>>>> > at least. (Does that even work in Gin? And can you put @Inject on an
>>>> > interface method?)
>>>> > What do you think?
>>>> > rjrjr
>>>> >
>>>> > --
>>>> > http://groups.google.com/group/Google-Web-Toolkit-Contributors
>>>>
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