firebase - 意外文本 "return"

Question

我正在尝试通过 Fireship ( https://fireship.io/lessons/flutter-firebase-google-oauth-firestore/ ) 教程实现 AuthService

我完全复制了他的 AuthService:

  AuthService() {
    user = Observable(_auth.onAuthStateChanged);

    profile = user.switchMap((FirebaseUser u) => {
      if (u != null) {
        return _db.collection("users").document(u.uid).snapshots().map((snap) => snap.data);
      } else {
        return Observable.just({});
      }
    });
  }

我收到这些错误:

如果我从他的网站上复制代码(完全一样)，就没有错误。卧槽有人可以解释一下或提供帮助吗？谢谢!

Answer 1

改变这个:

    profile = user.switchMap((FirebaseUser u) => {

进入这个:

    profile = user.switchMap((FirebaseUser u) {

来自docs :

For functions that contain just one expression, you can use a shorthand syntax:

bool isNoble(int atomicNumber) => _nobleGases[atomicNumber] != null;

The => expr syntax is a shorthand for { return expr; }. The => notation is sometimes referred to as arrow syntax.