3 Errors handling of Flutter(Dart)

catchError((e) => ~~~)

This is very popular error handling of Dart.

Example, This is the asynchronous function from Firestore.

Future<DocumentSnapshot> getUserInfo(String uid) {
   return Firestore.instance.collection("user").document(uid).get(); }

Error handling is like this.

getUserInfo(uid).then((value) {
     // success
 }).catchError((err) {
     // fails
})

try — catch

This error handling is try — catch pattern.

_setInitState() async {
    try {
      SharedPreferences preferences = await SharedPreferences.getInstance();
      String uid = await preferences.get("uid");
      User userInfo = await helper.getUserInfo(uid);
      SharedPreferences prefs = await SharedPreferences.getInstance();
      bool brightness = (prefs.getBool("isDark") ?? false);
      if (this.mounted) {
        setState(() {
          _uid = uid;
          _profileUrl = userInfo.iconUrl;
          _brightness = brightness;
        });
      }
    } catch (e) {
      // エラーハンドリング
    }

In this case, it is effective when handling errors with multi await.

Branch off builder

In this case, it is valid when FutureBuilder and StreamBuilder of Widget.

return FutureBuilder(
        future: helper.getUsersGroupList(_uid),
        builder: (context, snapshot) {

          if (snapshot.hasError) {
             // fail
          }

          // success
          final List<DocumentSnapshot> groupIdList = snapshot.data.documents;

          return ~~~~~ // functions when the asynchronous is success
        });

Summary

1. catchError((e) => ~~~~)
2. try - catch
3. Branch off builder

In my app, I handling errors all of them in these three ways.

Since Dart is influenced by JavaScript specifications, it is basically similar to JavaScript error handling, is not it??