Flutter : Avoid using `forEach` with a function literal - flutter

Question

Hi everyone this is my whole method :
Future<void> init() async {
FirebaseAuth.instance.userChanges().listen((user) {
if (user != null) {
_loginState = ApplicationLoginState.loggedIn;
_guestBookSubscription = FirebaseFirestore.instance
.collection('guestbook')
.orderBy('timestamp', descending: true)
.limit(3)
.snapshots()
.listen((snapshot) {
_guestBookMessages = [];
snapshot.docs.forEach((document) {
_guestBookMessages.add(
GuestBookMessage(
name: document.data()['name'] as String,
message: document.data()['text'] as String,
),
);
});
notifyListeners();
});
} else {
_loginState = ApplicationLoginState.loggedOut;
_guestBookMessages = [];
_guestBookSubscription?.cancel();
}
notifyListeners();
});
}
the part that dart complains about is this one :
snapshot.docs.forEach((document) {
_guestBookMessages.add(
GuestBookMessage(
name: document.data()['name'] as String,
message: document.data()['text'] as String,
),
);
});
how can I change this method without ruining the whole functionality ?
Im just looking for a way that makes dart happy .
I appreciate your help in advance.

Answer 1

AVOID using forEach with a function literal.
BAD:
snapshot.docs.forEach((document) {
...
});
GOOD:
for (var document in snapshot.docs) {
// Rest of your code
}

Answer 2

Using like data.forEach(function);
example:
void main() async {
List<int> list = [1, 2, 3, 4, 5];
//recommended
list.forEach(showSquareNumbers);
//not recommended
list.forEach((int number) => showSquareNumbers(number));
list.forEach((int number) {
showSquareNumbers(number);
});
}
void showSquareNumbers(int data) {
print("$data * $data = ${data * data}");
}
This is my opinion.
I think the forEach seems more complicated than the for loop and the forEach can't use continue and break (return is available but not a thing happens when using return).
void test(List data) {
data.forEach((element) {
print(element);
if(element) return;
});
for (var element in data) {
print(element);
if(element) continue;
if(element) break;
if(element) return;
}
}
I think we should use the for instead of the forEach loop when your forEach loop seems like this code below because the for loop have many options more than forEach as I said.
data.forEach((element) {
print(element)
});
//or
data.forEach((element) => print(element));
I think the forEach loop is used for short code (easy to understand) and when you want to do something you don't care about the result like this code (using with Function(dynamic)).
void test(List data) {
void showInTerminal(e) {
print("data is $e");
}
data.forEach(showInTerminal);
Function(dynamic) function = showInTerminal;
data.forEach(function);
}
Make sure the data type and function(type) are the same.
//error
void test(List<Map> data) {
void showInTerminal(String e) {
print("data is $e");
}
data.forEach(showInTerminal);
}
//success
void test(List<Map> data) {
void showInTerminal(Map e) {
print("data is $e");
}
data.forEach(showInTerminal);
}
I code like this. I think it's easy to read.
void test() {
dataList.forEach(removeData);
fileList.forEach(removeFile);
}

Answer 3

Use await for:
await for (final document in snapshot.docs) {
// Your code...
}