How to compare user input and the record in sqflite - flutter

Question

In sqflite database, I have a table called user. The user consists of username a, b, c.
When user enter the input var a, the system will compare with the username in table user. If user input equal to username in table user, system will print the error message, else the system will print success.
I try to use the future builder, but it didn´t work. How can I do the validation in Test.dart?
Thank you.
This is my code:
SqliteHelper.dart
Future getDat(UserAccount userAccount) async {
var dbClient = await db;
name = userAccount.username;
List<Map> result = await dbClient.query("UserAccount",
where: "username =?", whereArgs: [userAccount.username]);
if (result.length == 1) {
return name;
}
}
Test.dart
_saveData() async {
var db = UserAccountHelper();
var mynote = UserAccount(cTitle.text);
await db.getDat(mynote);
FutureBuilder(
future: db.getDat(mynote),
builder: (context, snapshot) {
if (snapshot.hasError) print(snapshot.error);
var data = snapshot.data;
if (snapshot.hasData) print("test 3");
if(snapshot.data.toString() == cTitle.text.toString())
{print("success")}
else{print("error")};
});
}

Answer 1

Future<String> getDat(String username) async {
var dbClient = await db;
List<Map> result = await dbClient.query("UserAccount",
where: "username =?", whereArgs: [username]);
if (result.length == 1) {
return name;
}
return null;
}
_saveData() async {
var db = UserAccountHelper();
var username = cTitle.text;
if(await db.getDat(username) != null) {
print('Error');
return;
}
print('Success');
}
Things I modified:
You don't need an UserAccount as parameter, because you use only the username from it.
The getDat returns null if the username isn't found in database;
In _saveData, if the result from the getDat is not null error is printed, else, success is printed.