Advanced sqflite Techniques in Flutter: Error handling

Error handling is an essential aspect of database operations in any programming language. In sqflite, there are several ways to handle errors that may occur during database operations to ensure that your app remains stable and provides a better user experience.

Try-Catch Blocks

One way to handle errors in sqflite is by using try-catch blocks. You can wrap your database operations in a try-catch block to catch any exceptions that might occur during the operation. This helps in identifying and handling the error in a controlled manner.

try {
  final db = await database;
  await db.insert(DatabaseHelper.table, row.toMap());
} catch (e) {
  print('Error inserting row: $e');
}

In the code above, we are using a try-catch block to catch any exceptions that might occur when inserting a row into the database. If an exception occurs, we are printing the error message to the console.

onError Callback

Another way to handle errors in sqflite is by using the onError callback. You can provide an onError callback to the Database constructor to handle any errors that might occur during database operations. This callback function is called whenever an error occurs during any database operation, providing a way to handle the error in a centralized location.

final db = await openDatabase(
  path,
  version: DatabaseHelper.version,
  onCreate: _onCreate,
  onUpgrade: _onUpgrade,
  onDowngrade: _onDowngrade,
  onError: (db, e) {
    print('Database error: $e');
  },
);

In the code above, we are providing an onError callback to the openDatabase constructor. If an error occurs during database operations, the onError callback will be called with the database instance and the error object.

Transactions

Transactions are a powerful way to ensure that a series of database operations are executed together as a single unit of work. Transactions in sqflite can also be used to handle errors. If an error occurs during a transaction, the transaction will be rolled back, and none of the changes will be committed to the database.

Future<void> transaction() async {
  final db = await database;
  try {
    await db.transaction((txn) async {
      await txn.insert(DatabaseHelper.table, row.toMap());
      await txn.update(DatabaseHelper.table, row.toMap(),
          where: '${DatabaseHelper.columnId} = ?', whereArgs: [row.id]);
    });
  } catch (e) {
    print('Error performing transaction: $e');
  }
}

In the code above, we are using a transaction to insert a row and update a row in the database. If an exception occurs during the transaction, the catch block will be called, and the transaction will be rolled back.

Futures

All database operations in sqflite return a Future object. You can handle errors by using the catchError method on the Future object. This is another way to handle errors in a more streamlined and organized manner.

Future<void> deleteRow(int id) async {
  final db = await database;
  await db.delete(
    DatabaseHelper.table,
    where: '${DatabaseHelper.columnId} = ?',
    whereArgs: [id],
  ).catchError((e) {
    print('Error deleting row: $e');
  });
}

In the code above, we are using the catchError method on the Future object returned by the delete method. If an error occurs during the operation, the catchError method will be called

Exception Handling

sqflite provides several built-in exception classes that you can use to handle errors in a more structured way. Some of the exception classes include SqfliteDatabaseException, SqfliteDatabaseLockedException, and SqfliteDatabaseReadOnlyException. These exception classes provide more specific information about the error that occurred.

try {
  final db = await database;
  await db.insert(DatabaseHelper.table, row.toMap());
} on SqfliteDatabaseException catch (e) {
  print('Database error: ${e.message}');
} catch (e) {
  print('Error inserting row: $e');
}

In the code above, we are using the SqfliteDatabaseException exception class to catch any database-related errors that might occur during the operation.

In conclusion, error handling is crucial in ensuring that your sqflite database operations are executed in a controlled and predictable manner. There are several techniques and approaches that you can use to handle errors, depending on your specific requirements and use case. By using a combination of try-catch blocks, callbacks, transactions, exceptions, and logging, you can build more robust and stable sqflite database apps.