Question

我有多个类对象，我想创建一个将任何类对象作为参数的独立函数。

这是我的收入阶层


    import 'package:finsec/model/dao.dart';

    class Income {
      int id, groupId, weekNumber, monthNumber, calendarYear;
      String frequency, payoutDate, category, depositTo, description, status;
      double expectedAmount, actualAmount;


      Income(
        this.id,
        this.groupId,
        this.expectedAmount,
        this.actualAmount,
        this.frequency,
        this.payoutDate,
        this.category,
        this.depositTo,
        this.status,
        this.weekNumber,
        this.monthNumber,
        this.calendarYear,
        [this.description]
      );
    }

这是我的费用类别对象


    import 'package:finsec/model/dao.dart';

    class Expense{
      int id, groupId
      String frequency, paidDate, expCategory,  description, status;
      double expectedAmount, actualAmount;


      Expense(
        this.id,
        this.groupId,
        this.expectedAmount,
        this.actualAmount,
        this.frequency,
        this.paidDate,
        this.expCategory,
        this.status,
        [this.description]
      );
    }


// The base class for the different types of items the list can contain.

    abstract class Dao<T> {
      //queries
      String get createTableQuery;

      //abstract mapping methods
      T fromMap(Map<String, dynamic> query);
      List<T> fromList(List<Map<String,dynamic>> query);
      Map<String, dynamic> toMap(T object);
    }


    import 'package:finsec/model/dao.dart';
    import 'package:finsec/model/income/income.dart';

    class IncomeDao implements Dao<Income> {

      @override
      Income fromMap(Map<String, dynamic> query) {
        Income income = Income();
        income.id = query["id"];
        income.groupId = query["groupId"];
        income.amount = query["amount"];
        income.frequency = query["frequency"];
        income.payoutDate = query["payoutDate"];
        income.category = query["category"];
        income.depositTo = query["depositTo"];
        income.status = query["status"];
        return income;
      }

      @override
      Map<String, dynamic> toMap(Income object) {
        return <String, dynamic>{
          "id": object.id,
          "groupId": object.groupId,
          "amount": object.amount,
          "frequency": object.frequency,
          "payoutDate": object.payoutDate,
          "category": object.category,
          "depositTo": object.depositTo,
          "status": object.status,
        };
      }

      @override
      List<Income> fromList(List<Map<String,dynamic>> query) {
        List<Income> income = List<Income>();
        for (Map map in query) {
          income.add(fromMap(map));
        }
        return income;
      }
    }

我想创建可以接收任何类对象的函数

 Future<int> insertTransaction(T object) async {
    var dao = new IncomeDao();
      dao.toMap(object));  
  }

基本上，我希望能够调用insertTransaction并传递任何类对象，然后将该对象传递给dao类。当我打电话给dao.toMap（object））;在insertTransaction函数中。我收到错误消息，例如“无法将参数类型'T'分配给参数类型'收入'。”

我猜flutter无法确定对象参数是收入还是费用等。我尝试使用诸如（收入）对象的转换，但没有用。

有人可以帮我吗？我试图重用我的函数（insertTransaction），而不是为每个对象类（例如收入，支出，事件等）创建相同的函数。

Answer 1

只需将T更改为动态

        public async Task GetCustomerAndRidesById_When_MultipleCustomersArePresent()
        {
            var connectionStringBuilder =
                new SqliteConnectionStringBuilder { DataSource = ":memory:" };
            var connection = new SqliteConnection(connectionStringBuilder.ToString());

            var options = new DbContextOptionsBuilder<TravelContext>()
                .UseSqlite(connection)
                .Options;

            var customer = _customerBuilder.WithDefaults();
            Customer customerFromRepo;

            using (var context = new TravelContext(options))
            {
                context.Database.OpenConnection();
                context.Database.EnsureCreated();

                await context.Customers.AddAsync(customer);

                await context.SaveChangesAsync();

                _output.WriteLine($"Customer ID: {customer.Id}");

                //var customerRepository = new CustomerRepository(context);
                //customerFromRepo = await customerRepository.GetByIdWithRidesAsync(customer.Id);
            }

            using (var context = new TravelContext(options))
            {
                var customerRepository = new CustomerRepository(context);
                try
                {
                    customerFromRepo = await customerRepository.GetByIdWithRidesAsync(customer.Id);
                }
                catch (System.Exception e)
                {
                    throw;
                }
            }

            customerFromRepo.Should().BeEquivalentTo(customer);
            customerFromRepo.Rides.Should().HaveCount(customer.Rides.Count);
        }

将不同的类对象传递给函数

1 个答案: