I've been thinking also about some kind of syntax like:
MyModule extends AbstractModule {
configure() { install(Multibindings.forModule(this)); }
@OptionalProvides(DEFAULT) Foo provideDefaultFoo(..) { .. }
@OptionalProvides(ACTUAL) Foo provideActualFoo(..) { .. }
@SetProvides Foo provideItemForSetOfFoo(..) { .. }
@MapProvides MapBinderEntry<Key, Foo> provideItemForMapOfKeyToFoo(..) { ..
}
}
... need to experiment and see if those pan out.
sam
On Wed, Apr 2, 2014 at 9:20 AM, Filipe Sousa <[email protected]> wrote:
> That's excellent
>
>
>
> On Wed, Apr 2, 2014 at 1:33 AM, Sam Berlin <[email protected]> wrote:
>
>> Ever wanted to:
>> 1) Set default binding in a library or framework that users can change?
>> 2) Inject something into a library or framework that isn't required,
>> but would be better if a user could set it?
>> 3) Inject an optional value into a constructor?
>>
>> OptionalBinder lets you do that. Christian just pushed out some of our
>> recent internal changes, including the introduction of OptionalBinder to
>> the multibindings extension.
>>
>> Some example usage:
>>
>> 1) Setting a default binding that a user can override:
>> Library: *OptionalBinder.newOptionalBinder(binder(), Foo.class)*
>> * .setDefault().to(DefaultFoo.class);*
>> At this point, code can inject '*Foo*' (or *Optional<Foo>)*, and will
>> get a *DefaultFoo.*
>>
>> User: *OptionalBinder.newOptionalBinder(binder(), Foo.class)*
>> * .setBinding().to(CustomFoo.class);*
>> Once a user calls setBinding(), injections of *Foo* (or
>> *Optional<Foo>)* will start providing *CustomFoo* instead.
>>
>> 2) Setting a binding that isn't required (e.g, no default value), but a
>> user can supply.
>> Library: *OptionalBinder.newOptionalBinder(binder(), Foo.class);*
>> At this point, code *can't* inject *Foo* -- it will fail saying the
>> binding isn't supplied. Code *can* (and should) inject *Optional<Foo>*,
>> though, and the optional will be absent.
>>
>> User: *OptionalBinder.newOptionalBinder(binder(), Foo.class)*
>> * .setBinding().to(CustomFoo.class);*
>> Once a user calls setBinding(), *Optional<Foo>* will be present and
>> supply the *CustomFoo*. Also, *Foo* can be directly injected now
>> (although only user could should do that, since the user code is the only
>> part that guarantees the binding will be there -- library code should still
>> inject the* Optional<Foo>*).
>>
>> Please report back if you have any issues or suggestions for improvement.
>>
>> Thanks!
>>
>> sam
>>
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>
>
>
> --
> Filipe Sousa
>
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