My custom command in my mod doesn't work.

[yliu7949]

Hello! I'm learning to develop a fabric mod now, and I use Kotlin instead of java.
I try to write a simple server-side mod for Minecraft 1.16.5. I wish players can receive the "Sing: message" by using the command "/sing <message>". The "/sing" command is a bit like the "/say" command.
My code :

package me.akiesky.chatwithqq

import com.mojang.brigadier.Command
import com.mojang.brigadier.CommandDispatcher
import com.mojang.brigadier.arguments.StringArgumentType.*
import net.fabricmc.api.ModInitializer
import net.fabricmc.fabric.api.command.v1.CommandRegistrationCallback
import net.minecraft.server.command.CommandManager.argument
import net.minecraft.server.command.CommandManager.literal
import net.minecraft.server.command.ServerCommandSource
import net.minecraft.text.LiteralText
import net.minecraft.text.Text

class ChatWithQQMod : ModInitializer {
    override fun onInitialize() {
        CommandRegistrationCallback.EVENT.register(
            CommandRegistrationCallback {
                    dispatcher: CommandDispatcher<ServerCommandSource?>, _: Boolean -> register(dispatcher)}
        )
    }
    private fun register(dispatcher: CommandDispatcher<ServerCommandSource?>) {
        dispatcher.register(literal("sing")
            .then(argument("message", greedyString()))
            .executes { context -> sing(context.source, getString(context,"message")) })
    }
    private fun sing(source : ServerCommandSource, message: String): Int {
        val text : Text = LiteralText("Sing：$message")
        source.sendFeedback(text,true)
        return Command.SINGLE_SUCCESS
    }
}

I ran the local server with IntelliJ IDEA, and connected to it with my Minecraft client.
I input the command /sing 123, no suggestion error. I entered and received the error :

Unknown or incomplete command, see below for error
sing 123<--[HERE]

I have read many tutorials and other mods' code. But I still cannot find where the problem is.

[haykam821]

You are closing the builder for the message argument too early for the executes to apply to it. Instead, the sing method will run for /sing only.

Instead, use this:

dispatcher.register(literal("sing")
	.then(argument("message", greedyString())
	.executes { context -> sing(context.source, getString(context,"message")) }))

[yliu7949]

Thanks a lot!