I'm quite new to Guice so perhaps I'm doing things wrong but I use this
pattern a lot:
@Inject
public MyClass(@Named("LowPricingStrategyA") IPricingStrategyA
pricingStrategyA,
ICalculator calculator) {
this.pricingStrategyA = pricingStrategyA ;
this.calculator = calculator;
}
then in the module:
protected void configure() {
bind(
IPricingStrategyA.class).annotatedWith(Names.named("LowPricingStrategyA")).to(LowPricingStrategyA.class);
bind(
IPricingStrategyA.class).annotatedWith(Names.named("HighPricingStrategyA")).to(HighPricingStrategyA.class);
bind( ICalculator.class).to(APRCalculator.class);
...
Note that for IPricingStrategyA I have two possible
bindings LowPricingStrategyA & HighPricingStrategyA, the module doesn't
know/specify which will be used, that is determined by
the @Named("LowPricingStrategyA") annotation in MyClass. Now imagine the
'pricing strategy group' has 5 pairs of classes A, B, C, D & E...a High and
a Low for each.
What I'm wondering is how to get the control of this centralized instead of
in 5 different classes.
-Dave
On Fri, Sep 14, 2012 at 8:25 AM, Stuart McCulloch <[email protected]> wrote:
> On 14 Sep 2012, at 15:16, Christian Gruber wrote:
>
> I feel like I need a bit more clarity of what you're trying to do before
> commenting properly. There are a few ways to think about what you describe
> here, but without a concrete example in code, it's hard to reason about
> what might be the best solution. Can you create a simplified example in
> code and paste it here, so we can better help?
>
>
> IMHO the real control should be in the module (ie. what gets bound to
> which key) and not in the concrete class - that should just declare what it
> needs (ie. its injected dependencies). If you have duplicate graphs of
> objects which only differ in price strategy then that sounds like the
> "robot-legs" problem:
> http://code.google.com/p/google-guice/wiki/FrequentlyAskedQuestions#How_do_I_build_two_similar_but_slightly_different_trees_of_objec
>
> On Friday, September 14, 2012 at 10:00 AM, dhoffer wrote:
>
> I've got a couple of projects that use Guice that used to use manual DI.
> So currently I have one module class with all the bindings. I often use
> the annotatedWith(Names.named("MyClass")) approach so I can specify which
> implementation should be injected.
>
> But this brings me to the problem. What if I have the case where several
> injections much change as a set? E.g. lets say I'm implementing a couple
> of pricing strategies where each strategy creates 5 concrete classes...it's
> critical that all 5 of those are from the same pricing strategy...not 4
> from one and 1 from another. In the old days, pre-Guice, I could just go
> to my 'application construction method' find the 5 relevant classes put
> them right next to each other in code...add comments/etc. E.g. everything
> was all in one place so it was manageable to find what types are being
> created and switch things out.
>
> Now post-Guice I have no centralized control of anything...as the module
> file doesn't say what is created it just says if 'you' find X use Y. The
> real control is in each java class file's @Inject constructor where I add
> the @Named("MyClass") annotation.
>
> How can I achieve a more centralized control over the exact classes
> instantiated?
>
>
>
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