Question

我正在编写我的第一个EventStore测试应用程序，我正在从流中重新保护我的对象，虽然它正确地获得了numberSold，但标题为null，我不明白为什么 - 从stream将标题设置为null，但我确信它写得很好。

一双新眼睛可以看到我做错了吗？

private static void Main()
{
    using (store = WireupEventStore())
    {
        var newBook = new Book("my book", 0);
        newBook.ChangeBookName("renamed book");
        newBook.AdjustBooksSold(5);
        var idToRetrieveLater = newBook.bookId;

        var bookRepo = new BookRepository(store);
        bookRepo.Put(newBook);

        var bookReadBack = bookRepo.Get(idToRetrieveLater);
        // book name is set to null here, but count==5 is OK
}

预订课程

public class Book
{ 
    public readonly Guid bookId;
    private int numberSold;
    private string title { get; set; }
    private List<object> eventsToCommit = new List<object>();

    public Book(string title, int sold)
    {
        this.bookId = Guid.NewGuid();
        this.title = title;
        this.numberSold = sold;
    }

    public Book(Guid id, IEnumerable<EventMessage> events)
    {
        this.bookId = id;
        foreach (var ev in events)
        {
            dynamic @eventToCall = ev.Body;
            Apply(@eventToCall);
        }
    }

    public void ChangeBookName(string name)
    {
        var nameChanged = new BookNameChanged(this.bookId, name);
        this.RaiseEvent(nameChanged);
    }

    public void AdjustBooksSold(int count)
    {
        var booksSold = new BookSold(this.bookId, count);
        this.RaiseEvent(booksSold);
    }

    private void Apply(BookNameChanged nameChanged)
    {
        this.title = nameChanged.title;
    }

    private void Apply(BookSold bookSold)
    {
        this.numberSold += bookSold.count;
    }

    protected void RaiseEvent(object eventToRaise)
    {
        dynamic @ev = eventToRaise;
        Apply(@ev);
        this.eventsToCommit.Add(eventToRaise);
    }

    public ICollection<object> GetEvents()
    {
        return this.eventsToCommit;
    }

    public void ResetEvents()
    {
        this.eventsToCommit = new List<object>();
    }
}

图书资料库

public class BookRepository
{
    IStoreEvents store;

    public BookRepository(IStoreEvents store)
    {
        this.store = store;
    }

    public void Put(Book book)
    {
        using (var stream = this.store.OpenStream(book.bookId, 0, int.MaxValue))
        {
            foreach (object o in book.GetEvents())
            {
                stream.Add(new EventMessage { Body = @o });
            }
            stream.CommitChanges(Guid.NewGuid());
            book.ResetEvents();
        }
    }

    public Book Get(Guid id)
    {
        using (var commits = this.store.OpenStream(id, 0, int.MaxValue))
        {
            var eventsToReply = commits.CommittedEvents;
            return new Book(id, eventsToReply);
        }
    }
}

命令

public class BookNameChanged
{
    public readonly Guid id;
    public readonly string title;

    public BookNameChanged(Guid id, string bookName)
    {
        this.id = id;
        this.title = bookName;
    }
}

public class BookSold
{
    public readonly Guid id;
    public readonly int count;

    public BookSold(Guid id, int count)
    {
        this.id = id;
        this.count = count;
    }
}

Answer 1

第一次去的好工作。根据您的连接方式，字段，它们是readonly以及缺少无参数公共构造函数的事实可能会导致大多数序列化机制出现问题 - 即使它们成为自动属性。

虽然我通常喜欢通过限制你的东西来保护不变量，但重要的是要平衡这一事实，一旦事件发生完全被烘焙 - 所以具有可写属性的POCO并不像你那样疯狂认为

我要做的另一件事就是摆脱事件中的ids。

（并加入DDD-CQRS邮件列表 - 最近的讨论触及了胖事件的概念 - 即重述可以从以前的事件中收集到的东西[基于您知道事件处理程序需要什么对事件做出反应]我同意这是一个坏主意。）

我必须发布我的AggregateBase - 你有正确的细微之处，但我会改变许多琐事。如果我没有早点完成，请在一周内戳我......

为什么我的命令事件字符串字段被检索为null

1 个答案: