With null safety enabled, I'm using the new dart version <2.18.1>.

this is my code

    import 'dart:async';
    import 'dart:io';

import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:untitled3/product.dart';

class ProductDBHelper{

  static final _databaseName = 'mydb.db';
  static final _databaseVersion = 1;

  static final _table_products = 'products';
  static String? path;

  ProductDBHelper._privateContructor();
  static final ProductDBHelper instance = ProductDBHelper._privateContructor();

  static Database? _database;

  ///////////// Check whether the database created or not ...........
  Future get database async{

    if(_database != null) return _database;

    _database = await _initDatabase();
    return _database;
  }

  //////////////////////////Inittalize database with lile path, db name .............
  _initDatabase() async{

    Directory documentDirectory = await getApplicationDocumentsDirectory();
    ///////// Localstorage path/databasename.db
    String path = join(documentDirectory.path , _databaseName);
    return await openDatabase(
      path,
      version: _databaseVersion,
      onCreate: _onCreate);
  }

  ///////////////////// On Create for creating datadase ........................
  FutureOr _onCreate(Database db, int version) async{

    await db.execute('CREATE TABLE $_table_products(id INTEGER PRIMARY KEY autoincrement, name TExt , price TEXT, quantity INTEGER)');
  }

  static Future getfileData() async
  {
    return getDatabasesPath().then((value)
    {
      return path = value;
    }
    );
  }

  Future insertProduct(Product product) async {
    Database db = await instance.database;
    return await db.insert( _table_products, Product.toMap(product) , conflictAlgorithm: ConflictAlgorithm.ignore);
  }


  Future<List<Product>> getProductList() async{

    Database db = await instance.database;
    List<Map> maps = await db.query(_table_products);
    print(maps);
    return Product.fromMapList(maps);
  }

  Future<Product> updateProduct(Product product) async{

    DatabaseException db = await instance.database;

    await db.update(_table_products, Product.toMap(product) , where: 'id = ?'
    , whereArgs: [product.id]);

    return product;
  }
  Future deleteProduct(Product product) async {
    DatabaseException db = await instance.database;

    var deletedProduct = await db.delete(_table_products, where: 'id = ?'
        , whereArgs: [product.id]);

    return product;
  }
}

I'm getting these errors:

The method 'update' isn't defined for the type 'DatabaseException'.

The method 'delete' isn't defined for the type 'DatabaseException'.

and this error in the Run log:

lib/product_db_helper.dart:76:14: Error: The method 'update' isn't defined for the class 'DatabaseException'.

• 'DatabaseException' is from 'package:sqflite_common/src/exception.dart' ('../../Documents/flutter/Flutter/flutter_windows_3.3.2-stable/flutter/.pub-cache/hosted/pub.dartlang.org/sqflite_common-2.3.0/lib/src/exception.dart'). Try correcting the name to the name of an existing method, or defining a method named 'update'. await db.update(_table_products, Product.toMap(product) , where: 'id = ?' ^^^^^^ lib/product_db_helper.dart:84:35: Error: The method 'delete' isn't defined for the class 'DatabaseException'.
• 'DatabaseException' is from 'package:sqflite_common/src/exception.dart' ('../../Documents/flutter/Flutter/flutter_windows_3.3.2-stable/flutter/.pub-cache/hosted/pub.dartlang.org/sqflite_common-2.3.0/lib/src/exception.dart'). Try correcting the name to the name of an existing method, or defining a method named 'delete'. var deletedProduct = await db.delete(_table_products, where: 'id = ?' ^^^^^^

    Future<Product> updateProduct(Product product) async{

    DatabaseException db = await instance.database;

    await db.//update//(_table_products, Product.toMap(product) , where: 'id = ?'
    , whereArgs: [product.id]);

    return product;
  }
  Future deleteProduct(Product product) async {
    DatabaseException db = await instance.database;

    var deletedProduct = await db.//delete//(_table_products, where: 'id = ?'
        , whereArgs: [product.id]);

    return product;
  }

This is where the errors appear. I put // where the red underlines are. Please help me.

CodePudding user response：

in your updateProduct function,

Change This

DatabaseException db = await instance.database;

to this

Database db = await instance.database;