Jump to content

[1.9.4] [!Solved!] Scala-friendly capabilities system?


Recommended Posts

I'm working on a magic-mod in Scala.  While it's taken me a long time to get up to speed on ye ole minecraft APIs, I just realized that perhaps a lot of things I'm doing should be exposed as capabilities (or could be better expressed as such).


There is on particular sticking point:  Right now,


instances are injected to static final values.  Scala isn't really friendly with static variables (prefering object instances instead).


So, would the minecraft forge folks be ammenable to some kind of "Lookup capability" (NOT implemented via injection) that I can hide behind some scala, like:


object MyMod {
    lazy val MyCapability = Capabilties.INSTANCE.lookUp(CapabilityName)


Alternatively, could we adapt the injection code to allow scala objects?  While (unfortunately) there's no marker trait for these, you can detect them via these assumptions:


  • The class name ends with

  • The class name contains a single static field called


Does anyone know of any mechanism I could use to implement capabilities in Scala?  I'm specifically trying to attach data to player entities, and Capabilities seem like the "right" way to do it, vs. the random hackery I'm using now.

Link to comment
Share on other sites

Yes, I understand the benefits of private static final in the JVM.  It's not really an option for Scala (until 2.12) as there is no way to generate static fields.


I did find a workaround though, I can define the private final field in a Java file and expose everything I need to scala.  I had thought the inject annotation wouldn't work unless the field was defined in the mod, which is not, apparently, the case.


Sorry for the noise!

Link to comment
Share on other sites

Wow, uh thanks.  I'd ask what code is stupid, but I assume you mean all Scala.  I'm happy to use the Java APIs, I was just curious on this one, as it's the only instance so far I've found where there was any deviation at all (and kudos for how amazing forge is, it's been a breeze getting started in Scala).


I was able to craft some scala with the annotation on my singleton instance, but unfortunately it's not injected.


import scala.annotation.meta.field
type ScalaCapabilityInject = CapabilityInject @field
private final val Cap: Capability[PlayerWaypoints] = null


I validated the bytecode has the annotation appropriately, but it's probably something silly which is not letting the ASM table find it.  Oh well.


For now I have a workaround that's fine.  I'll just have one Java file to test all my capabilities.


I'm still a bit confused by the Capability "Factory" though, so I'll start a new thread for that. 


I'll mark this closed (or does a mod do that?)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

By using this site, you agree to our Terms of Use.