Add syntactic sugar for mapping a class to itself

[creynders]

ATM if you want to map a class to be instantiated afresh each time you need to do:

injector.map(FooClass).toType(FooClass);

Maybe it would be a good idea to add this to the API:

injector.map(FooClass).asType();

It's in symmetry with

injector.map(FooClass).asSingleton();

@darscan What ya think?

[creynders]

See robotlegs/robotlegs-framework#151

[darscan]

Can't you just do this: injector.map(FooClass);

[creynders]

Ummm... Do you mean that is how it already works? Or as a suggestion of how it could work?
If the former, I didn't realize that.

[creynders]

It does break the symmetry, no? And it's not really clear either.

[darscan]

I believe that's how it currently works. I'm not fond of it myself.

[creynders]

Ok, I'll test it out. Would you agree on adding InjectionMapping#asType for clarity (and obsessive compulsive disorder soothing medicine)?

[darscan]

Sounds good to me :)

[tschneidereit]

That's exactly how it already works. But I agree: adding
InjectionMapping#asType makes a lot of sense, if only for symmetry's sake.

[creynders]

🤘

[Stray]

wades in

is there something better than: asType() ?

'asType' always bothered me - because when do you map something not as a type? So it kind of means "not special", which is a very icky bit of venn diagram labelling.

IIRC, it means newInstanceEachTimeFreshlyConstructedByTheAppropriateInjector() ... which obviously sucks, but perhaps there is something both pithy and less opaque than 'asType'?

Sx

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[creynders]

@Stray Yeez. Unfortunately you're quite right.

[creynders]

asNothingSpecial

[creynders]

asNotSingleton

[creynders]

@tschneidereit I just took a quick look and was wondering why exactly it's done like this in the InjectionMapping constructor?

_defaultProviderSet = true;
mapProvider(new ClassProvider(type));

Seems a bit wasteful to have a ClassProvider instance created for each mapping, only to be thrown away in 90% of the cases.
Was it for robustness? Making sure nothing explodes if someone writes injector.map(FooClass) and forgets to map it to something.
What happens with interfaces though? And wouldn't it be preferable to have it explode?

[tschneidereit]

@tschneidereit https://github.com/tschneidereit I just took a quick look
and was wondering why exactly it's done like this in the
InjectionMappingconstructor?

_defaultProviderSet = true;mapProvider(new ClassProvider(type));

Seems a bit wasteful to have a ClassProvider instance created for each
mapping, only to be thrown away in 90% of the cases.
Was it for robustness? Making sure nothing explodes if someone writes
injector.map(FooClass) and forgets to map it to something.
What happens with interfaces though? And wouldn't it be preferable to have
it explode?

It will explode for interface, but later. I agree that this is a bit
unfortunate.

I went back and forth on this quite a bit. In the end, I decided that I'd
roughly go with what other frameworks do, and make using instance-factory
providers easy. See, it doesn't look like this will be thrown away 90% of
the time. That, combined with ClassProvider being very cheap and
injection mapping usually not being on hot paths made me go with this
setup. If I remember everything correctly, that is.

Another consideration is that, without setting a default, it's pretty easy
to leave mappings in an unfinished state, in which case they'll blow up
later. Whether that is worse than automatically, and perhaps unexpectedly,
injecting new instances, I don't know.

@darscan was talking about the ability to "finish" an injector, making it
impossible to add more mappings, or change existing ones. Besides
potentially enabling some optimizations, that would make it trivial to
check for unfinished mappings and throw for them. A weaker version of this
would be to introduce a verifyMappings method in Injector, to be called
when one assumes all mappings to be complete.