[1.15.2] Storing player location for a 'measure' command

[Cecil]

Hello! I'm just getting into modding, and am starting by adding commands. I have the Brigadier system figured out, and have a few basic test commands working.

I'd like to create a 'measure' command next that would be called once to define a starting location, and again to calculate the measurement and return that to the player.

In order to store the first location, I'm imagining somehow storing a 'measurement start position' with the player, but I'm not sure how best to go about it. Or would another approach be better?

[Cecil]

An easy answer, thank you!

[Cecil]

Alright, I have a functioning measure command! Some of the previous forum posts were very helpful in understanding capabilities, but there's still a few things I'm not quite clear on.

 

Particularly in my Provider:

public class MeasurementProvider implements ICapabilityProvider {
    @CapabilityInject(IMeasurement.class)
    public static final Capability<IMeasurement> MEASUREMENT_CAPABILITY = null;

    private final LazyOptional<IMeasurement> instance = LazyOptional.of(Measurement::new);

    @Nonnull
    @Override
    public <T> LazyOptional<T> getCapability(@Nonnull Capability<T> cap, @Nullable Direction side) {
        return cap == MEASUREMENT_CAPABILITY ? instance.cast() : LazyOptional.empty();
    }
}

 

This is mostly based on others code examples, and it does work. What I don't understand is how getCapability() is working. You pass it a Nonnull Capability "cap", and then compare that to MEASUREMENT_CAPABILITY, which is null. Further, this is how I'm calling getCapability (in part):

getCapability(MeasurementProvider.MEASUREMENT_CAPABILITY, null)

Isn't this passing a Null argument to what should be a Nonnull parameter?

 

Maybe this just displays a lack of Java knowledge on my part, in which case I'll keep looking into it myself, but if there's something about the capability system I'm missing I would appreciate any help. Thanks!

[poopoodice]

@CapabilityInject

https://mcforge.readthedocs.io/en/latest/datastorage/capabilities/#using-an-existing-capability

Quote

This annotation can be applied to fields and methods. When applied to a field, it will assign the instance of the capability (the same one gets assigned to all fields) upon registration of the capability

 

[Cecil]

Got it, that makes sense. Thank you!