How can I make Cirqus stop automatically creating new instances? - cqrs

Question

I have an aggregate root with a few events and commands. One of those commands is a CreateCommand. That command should create a new aggregate root with a given ID. Every other event/command should just update an existing aggregate root and fail if the aggregate root with the given ID doesn't exist.
How can I make Cirqus work this way?
This is how I configure my CommandProcessor:
var commandProcessor = CommandProcessor
.With()
#if DEBUG
.Logging(l =>
{
if (_useConsoleForLogging)
{
l.UseConsole(Logger.Level.Debug);
}
else
{
l.UseDebug(Logger.Level.Debug);
}
})
#endif
.EventStore(e => e.UseSqlServer(_connectionString, _eventsTableName))
.EventDispatcher(e => e.UseViewManagerEventDispatcher(viewManagers))
.Create();
This is the CreateCommand:
public class CreateCommand : ExecutableCommand
{
public CreateCommand()
{
CreatedGuid = Guid.NewGuid();
}
public Guid CreatedGuid { get; }
public override void Execute(ICommandContext context)
{
var root = context.Create<MyAggregateRoot>(CreatedGuid.ToString());
}
}
Of course this CreateCommand contains more code that emits a few events to immediately update some properties of the created instance, but I've removed them as they're not vital to this question.

Answer 1

You can do that by using ExecutableCommand to implement your own update command - you could call it UpdateCommand.
It could look something like this:
public abstract class UpdateCommand<TAggregateRoot>
{
readonly string _aggregateRootId;
protected UpdateCommand(string aggregateRootId)
{
_aggregateRootId = aggregateRootId;
}
public override void Execute(ICommandContext context)
{
var instance = context.Load<TAggregateRoot>(_aggregateRootId);
Update(instance);
}
public abstract void Update(TAggregateRoot instance);
}
and then all commands derived off of UpdateCommand would experience exceptions if they tried to address non-existing instances.
Similarly, you could ensure creation with a CreateCommand base class that would use ICommandContext's Create<TAggregateRoot> method to ensure that an existing instance was not accidentally being addressed.