Initialized database still returns as null [Flutter, sqflite] - flutter

Question

I'm trying to perform CRUD operations on Flutter, using the sqflite library. Online resources point towards a bunch of ways to go about this. Here is my implementation:
class SqlManager {
static const String tname = 'table1';
static const String dname = 'database.db';
Future<Database> db;
initDB() async {
Directory path = await getApplicationDocumentsDirectory();
db = openDatabase(join(path.path, dname), version: 1, onCreate: (db, version) {
return db.execute(
'CREATE TABLE $tname (id INTEGER PRIMARY KEY, name TEXT, type TEXT, time1 INTEGER, time2 INTEGER, imp INTEGER, urg INTEGER)');
});
}
Future<void> writing(Task task) async {
print("called");
final Database DB = await db;
await DB.insert(
tname,
task.toMap(),
conflictAlgorithm: ConflictAlgorithm.replace,
);
print("Execution completed");
}
Future<List<Task>> reading() async {
Database DB = await db;
List<Map<String, dynamic>> maps = await DB.query(tname);
return List.generate(maps.length, (i) {
return Task.fromMap(maps[i]);
});
}
}
Whenever I attempt to call any of these functions, I hit upon a NoSuchMethodError, thrown by the variable 'DB' inside one of these functions. Any help is appreciated, thanks!

Answer 1

Whenever I attempt to call any of these functions, I hit upon a NoSuchMethodError, thrown by the variable 'DB' inside one of these functions. Any help is appreciated, thanks!
It's because you haven't initialized your database by calling the initDB(). So, call it before you call the method using the database. But you'll end with recreating each instance for each call.
The better way is by creating a singleton for your database. Modify your SqlManager to something like this:
class SqlManager {
static const String tname = 'table1';
static const String dname = 'database.db';
// Future<Database> db;
// Make a singleton class
SqlManager._privateConstructor();
static final SqlManager instance = SqlManager._privateConstructor();
// Use a single reference to the db.
static Database _db;
// Use this getter to use the database.
Future<Database> get database async {
if (_db != null) return _database;
// Instantiate db the first time it is accessed
_db = await _initDB();
return _db;
}
// Init the database for the first time.
_initDB() async {
Directory path = await getApplicationDocumentsDirectory();
return await openDatabase(join(path.path, dname), version: 1, onCreate: (db, version) {
return db.execute(
'CREATE TABLE $tname (id INTEGER PRIMARY KEY, name TEXT, type TEXT, time1 INTEGER, time2 INTEGER, imp INTEGER, urg INTEGER)');
});
}
// Then you can use the database getter in another method
Future<List<Task>> reading() async {
Database DB = await instance.database;
List<Map<String, dynamic>> maps = await DB.query(tname);
return List.generate(maps.length, (i) {
return Task.fromMap(maps[i]);
});
}
}