How to use

getSourceId

method

in

mage.abilities.keyword.GravestormAbility

@Override
public boolean checkTrigger(GameEvent event, Game game) {
  if (event.getSourceId().equals(this.getSourceId())) {
    StackObject spell = game.getStack().getStackObject(this.getSourceId());
    if (spell instanceof Spell) {
      for (Effect effect : this.getEffects()) {
        effect.setValue("GravestormSpell", spell);
        effect.setValue("GravestormSpellRef", new MageObjectReference(spell.getId(), game));
      }
      return true;
    }
  }
  return false;
}