Step 3. Add custom action

Here is my code example.

public class ActSetClass extends AbstractAction { //Action class must be extended class of kor.toxicity.questadder.api.mechanic.AbstractAction
    //Data field must be annotated by kor.toxicity.questadder.api.util.DataField
    @DataField(aliases = "n", throwIfNull = true) //aliases = an field name aliases, throwIfNull = making an error when this field is null
    public String name; //Data field must be public

    public ActSetClass(@NotNull QuestAdder adder) {
        super(adder);
    }

    @Override
    public void invoke(Player player //A player that run action, QuestAdderEvent questAdderEvent //A event that run action) {
        var data = Fantasia.Companion.getPlayerData(player);
        if (data != null) {
            data.setClazz(name);
            Fantasia.Companion.loadOption(player);
        }
    }
}

QuestAdderAPI.getInstance().apiManager.addAction("setclass", ActSetClass::class.java)

it actually works like this:

- setclass{n=knight}