eventFlow 系列 <二> 领域事件

看一个聚合根：

  public class ExampleAggregate :
        AggregateRoot<ExampleAggregate, ExampleId>,
        IEmit<ExampleEvent>
    {
        private int? _magicNumber;
        private int NameExample;

        public ExampleAggregate(ExampleId id) : base(id) { }

        // Method invoked by our command
        public IExecutionResult SetMagicNumer(int magicNumber,int n)
        {
            if (_magicNumber.HasValue)
                return ExecutionResult.Failed("Magic number already set");

            Emit(new ExampleEvent(magicNumber, n));
            
            return ExecutionResult.Success();
        }

        // We apply the event as part of the event sourcing system. EventFlow
        // provides several different methods for doing this, e.g. state objects,
        // the Apply method is merely the simplest
        public void Apply(ExampleEvent aggregateEvent)
        {
            _magicNumber = aggregateEvent.MagicNumber;
            NameExample = aggregateEvent.NameExample;
        }
    }

实现了IEmit 接口，那么

Emit(new ExampleEvent(magicNumber, n));
这句话执行的时候，
就会触发领域事件的执行。

这个Emit 是AggregateRoot 的方法。在AggregateRoot  的Emit  方法中，调用apply 方法。

下面是ReadModel ，实现了 IAmReadModelFor<ExampleAggregate, ExampleId, ExampleEvent> 接口

public class ExampleReadModel :
        IReadModel,
        IAmReadModelFor<ExampleAggregate, ExampleId, ExampleEvent>
    {
        public int MagicNumber { get; private set; }
        public int NameExample { get; private set; }
        public void Apply(IReadModelContext context, IDomainEvent<ExampleAggregate, ExampleId, ExampleEvent> domainEvent)
        {
            MagicNumber = domainEvent.AggregateEvent.MagicNumber;
            NameExample = domainEvent.AggregateEvent.NameExample;
        }
    }