Poco Aggregate Root braindump

gistfile1.mkd

Intro

This is just an braindrump and rolling gist that reflect the thought about POCO support for Ncqrs.

The Poco object

1. Contain typed event handling methods like OnCustomerNameChanged(NameChanged e) that update internal state.
2. Contains a Guid ID property. This will hold the event source id.
3. Contains one ctor for 'new' instances that only accepts an Func callback.
4. Contains one ctor to support loading from history. This ctor has two parameters. On Func callback and an Guid value with the existing id.

So minimal code is:

public class TestPocoAggregateRoot
{
    private readonly Action<ISourcedEvent> ApplyEvent;
    public Guid Id { get; private set; }

    private int _state;

    public TestPocoAggregateRoot(Guid id, Action<ISourcedEvent> applyEvent) : this(applyEvent)
    {
        Id = id;
    }

    public TestPocoAggregateRoot(Action<ISourcedEvent> applyEvent)
    {
        ApplyEvent = applyEvent;
    }

    public void DoSomething(int arguments)
    {
        ApplyEvent(new SomethingDone{ Value = arguments * 42 });
    }

    protected void OnSomethingDone(SomethingDone evnt)
    {
        _state += evnt.Value;
    }
}

public class SomethingDone : SourcedEvent
{
    public int Value { get; set; }
}