检查谁是第一个在 firebase firestore 中设置属性的正确方法

Question

I'm creating a game using firebase firestore, and I need to tell which user started the game. The idea that I had was to have a startedByPlayer: string property and use a transaction to update this property. If this property is already set, then eventually return false; otherwise, set this property with the current user and eventually return true.

Since it's tough to test race conditions, I just wanted to make sure this was the right approach:

function tryToStartGame(player : Player) {
  const ref = gamesRef.doc("game");
  return db.runTransaction(function (transaction) {
    return transaction.get(ref).then(function (game) {
      if (!game.exists) {
        return false;
      }

      const { startedByPlayer: startedByUser } = game.data() as Game;

      if (!startedByUser) {
        transaction.update(ref, { startedByUser: player.id });
        return true;
      }

      return false;
    });
  });
}

Answer 1

Yes, this is a great idea, indeed. Checking this way, it will cover already started games, so values are not replaced and no unnecessary writes are made or set the value properly, in case needed. And besides that, you have a function that will confirm via boolean, the creation, if either happened in that moment or if it was already done. So, I think you are covering needed points, in a not so complex model for you to program.

I hope this information helps clarifies your doubts!