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dog.toMap(),
// Ensure that the Dog has a matching id.
where: 'id = ?',
// Pass the Dog's id as a whereArg to prevent SQL injection.
whereArgs: [dog.id],
);
}<code_end>
<code_start>// Update Fido's age and save it to the database.
fido = Dog(
id: fido.id,
name: fido.name,
age: fido.age + 7,
);
await updateDog(fido);
// Print the updated results.
print(await dogs()); // Prints Fido with age 42.<code_end>
warning Warning
Always use whereArgs to pass arguments to a where statement.
This helps safeguard against SQL injection attacks.Do not use string interpolation, such as where: "id = ${dog.id}"!<topic_end>
<topic_start>
8. Delete a Dog from the database
In addition to inserting and updating information about Dogs,
you can also remove dogs from the database. To delete data,
use the delete() method from the sqflite library.In this section, create a function that takes an id and deletes the dog with
a matching id from the database. To make this work, you must provide a where
clause to limit the records being deleted.
<code_start>Future<void> deleteDog(int id) async {
// Get a reference to the database.
final db = await database;
// Remove the Dog from the database.
await db.delete(
'dogs',
// Use a `where` clause to delete a specific dog.
where: 'id = ?',
// Pass the Dog's id as a whereArg to prevent SQL injection.
whereArgs: [id],
);
}<code_end>
<topic_end>
<topic_start>
Example
To run the example:
<code_start>import 'dart:async';
import 'package:flutter/widgets.dart';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
void main() async {
// Avoid errors caused by flutter upgrade.
// Importing 'package:flutter/widgets.dart' is required.
WidgetsFlutterBinding.ensureInitialized();
// Open the database and store the reference.
final database = openDatabase(
// Set the path to the database. Note: Using the `join` function from the
// `path` package is best practice to ensure the path is correctly
// constructed for each platform.
join(await getDatabasesPath(), 'doggie_database.db'),
// When the database is first created, create a table to store dogs.
onCreate: (db, version) {
// Run the CREATE TABLE statement on the database.
return db.execute(
'CREATE TABLE dogs(id INTEGER PRIMARY KEY, name TEXT, age INTEGER)',
);
},
// Set the version. This executes the onCreate function and provides a
// path to perform database upgrades and downgrades.
version: 1,
);
// Define a function that inserts dogs into the database
Future<void> insertDog(Dog dog) async {
// Get a reference to the database.
final db = await database;
// Insert the Dog into the correct table. You might also specify the
// `conflictAlgorithm` to use in case the same dog is inserted twice.
//
// In this case, replace any previous data.
await db.insert(
'dogs',
dog.toMap(),
conflictAlgorithm: ConflictAlgorithm.replace,
);
}
// A method that retrieves all the dogs from the dogs table.
Future<List<Dog>> dogs() async {
// Get a reference to the database.
final db = await database;
// Query the table for all the dogs.
final List<Map<String, Object?>> dogMaps = await db.query('dogs');
// Convert the list of each dog's fields into a list of `Dog` objects.
return [
for (final {
'id': id as int,
'name': name as String,
'age': age as int,
} in dogMaps)
Dog(id: id, name: name, age: age),
];
}
Future<void> updateDog(Dog dog) async {
// Get a reference to the database.
final db = await database;