Function expressions can't be named. doc error - flutter

Question

Hello in my flutter project i got this problem when i want to recall users by thier ID.
Future<UserModel> getUserById(String id)=> _firestore.collection(collection).doc(id){
print("==========id is $id=============");
debugPrint("==========NAME is ${doc.data()['name']}=============");
debugPrint("==========NAME is ${doc.data()['name']}=============");
it gives an error on [ .doc(id){ ]
what shall i do?
an also in my order page it gives same error somehow
_firestore.collection(collection).doc(id).setData()({
"userId": userId,
"cart": convertedCart,
"id": id,
"total": totalPrice,
"createdAt": DateTime.now().millisecondsSinceEpoch,
"description": description,
"status": status
});
}
what do you guys think?
in that line
_firestore.collection(collection).doc(id).setData()({
setData is error
my flutter version is 2.5.1

Answer 1

Try the code below.
Future<UserModel> getUserById(String id){
return FirebaseFirestore.instance.collection("collectionPath")
.doc(id).get().then((doc) => UserModel.fromSnapShot(doc.data()));
}
Your fromSnapshot don't return a UserModel. It should look like this.
import 'package:flutter/foundation.dart';
#immutable
class UserModel{
final String id;
final String name;
final String email;
final String stripeId;
final List<CartItemModel> cart;
final int totalCartPrice;
const UserModel({required this.id, required this.name, required this.email, required this.stripeId, required this.cart,
required this.totalCartPrice});
Map<String, dynamic> toMap() {
return {
'id': id,
'name': name,
'email': email,
'stripeId': stripeId,
'cart': cart,
'totalCartPrice': totalCartPrice,
};
}
factory UserModel.fromMap(Map<String, dynamic> map) {
return UserModel(
id: map['id'] as String,
name: map['name'] as String,
email: map['email'] as String,
stripeId: map['stripeId'] as String,
cart: (map['cart'] as List).map((cart) => CartItemModel.fromMap(cart)).toList() ,
totalCartPrice: map['totalCartPrice'] as int,
);
}
}
#immutable
class CartItemModel{
final String id;
const CartItemModel({required this.id});
Map<String, dynamic> toMap() {
return {
'id': id,
};
}
factory CartItemModel.fromMap(Map<String, dynamic> map) {
return CartItemModel(
id: map['id'] as String,
);
}
}