Best way to return a "success" text for a @LuaFunction?

[Lordmau5]

Hey there!

I'm currently working on implementing CC support in my mod FFS again and was curious about something.

I already figured out that I can throw a LuaException when something isn't as it should, e.g. my tank being invalid.

I wonder if there's something similar for a method to return that it succeeded?

For example, I have a method to lock the fluid in the tank and when it locks it I would like to return a string along the lines of "Locked fluid to [FLUID_NAME].".

If this is not intended and I should rather just return a boolean on whether it succeeded or not I'd be fine with that, but I just wasn't sure what the commonly accepted way for this is :)

[SirEdvin]

I am not sure, that there is a commonly accepted way for this, but I can suggest to use something like Result Monad, which is effectefly just returning table {isOperationSuccessful, problemWithOperation} and return exception only in cases of invalid output of some incorrect usage of function

Update: Not a table, just one or two values for easly handle like in golang:

local result, err = true, "haha"

if err ~= nil then
print(err)
end

[Lordmau5]

How would I return a table in that case? Do I set my method return type to LuaTable and then build a map with the results?

Because that'd be quite nice to have for a different method I have to get the tank info haha

[SquidDev]

You can return a Map<?, ?> to represent a Lua table. See the docs from MethodResult:

CC-Tweaked/projects/core-api/src/main/java/dan200/computercraft/api/lua/MethodResult.java

Lines 51 to 58 in d066d17

	* Return a single value immediately.
	* <p>
	* Integers, doubles, floats, strings, booleans, {@link Map}, {@link Collection}s, arrays and {@code null} will be
	* converted to their corresponding Lua type. {@code byte[]} and {@link ByteBuffer} will be treated as binary
	* strings. {@link ILuaFunction} will be treated as a function.
	* <p>
	* In order to provide a custom object with methods, one may return a {@link IDynamicLuaObject}, or an arbitrary
	* class with {@link LuaFunction} annotations. Anything else will be converted to {@code nil}.

and LuaFunction:

CC-Tweaked/projects/core-api/src/main/java/dan200/computercraft/api/lua/LuaFunction.java

Lines 18 to 36 in d066d17

	* Methods annotated with {@link LuaFunction} must be public final instance methods. They can have any number of
	* parameters, but they must be of the following types:
	*
	* <ul>
	* <li>{@link ILuaContext} (and {@link IComputerAccess} if on a {@link IPeripheral})</li>
	* <li>{@link IArguments}: The arguments supplied to this function.</li>
	* <li>
	* Alternatively, one may specify the desired arguments as normal parameters and the argument parsing code will
	* be generated automatically.
	* <p>
	* Each parameter must be one of the given types supported by {@link IArguments} (for instance, {@link int} or
	* {@link Map}). Optional values are supported by accepting a parameter of type {@link Optional}.
	* </li>
	* </ul>
	* <p>
	* This function may return {@link MethodResult}. However, if you simply return a value (rather than having to yield),
	* you may return {@code void}, a single value (either an object or a primitive like {@code int}) or array of objects.
	* These will be treated the same as {@link MethodResult#of()}, {@link MethodResult#of(Object)} and
	* {@link MethodResult#of(Object...)}.

Though typically here you wouldn't return a table and would return multiple values (so new Object[] { success, message }).

[Lordmau5]

Sweet! Thank you guys!

[SirEdvin]

I usually just return MethodResult.of(isOperationSuccessful, problemWithOperation) like here.

Oh, I see know, that I make a huge mistake in my first comment. This is not a table, it is just two values (or single, eventually)

[SirEdvin]

Sorry for this mistake :(