OneOfAttribute

[OneOf(types)] attribute is a way to define one-of cases in a class.

[OneOf(typeof(Result), typeof(Error), typeof(NoResult))]
public interface IMessage
{
    public sealed class Result : IMessage { }
    public sealed class Error : IMessage { }
    public sealed class NoResult : IMessage { }
}

AccessorRequest(target) requests for IAccessor depending on type target.

// Create service
IService service = Services.Create(NetAccessorHandlers.Instance);
// Create container target
IContainerTarget target = new NetOneOf(typeof(IMessage));
// Create request
IRequestFor<IAccessor> request = new AccessorRequest(target);
// Issue request
IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);

OneOfAccessorRequest(target) requests for IOneOfAccessor<OneOf, Element>.

// Create service
IService service = Services.Create(NetAccessorHandlers.Instance);
// Create container target
IContainerTarget target = new NetOneOf(typeof(IMessage));
// Create request
IRequestFor<IOneOfAccessor> request = new OneOfAccessorRequest(target);
// Issue request
IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);

OneOfAccessorRequest is specifically a request for specific writers. Each can be assigned with explicit customization.

// Create service
IService service = Services.Create(NetAccessorHandlers.Instance);
// Create container target
IContainerTarget target = new NetOneOf(typeof(IMessage));
// Create request
IRequestFor<IOneOfAccessor> request = new OneOfAccessorRequest
{
    Constructor = new ConstructorRequest(target),
    Deconstructor = new DeconstructorRequest(target),
    DefaultConstructor = new DefaultConstructorRequest(target),
    Fields = new ContentAccessorsRequest(target),
    IsAssigned = new IsAssignedRequest(target),
    Unassign = new UnassignRequest(target),
    ContainerType = new ContainerTypeRequest(target),
    ContentType = new ContentTypeRequest(target),
};
// Issue request
IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);

Usage

.DefaultConstructor creates a oneof with default value.

IMessage oneOf = accessor.DefaultConstructor.Read();

.Constructor creates a oneof from enumerable of elements.

IMessage oneOf = accessor.Constructor.ReadAs<(int tag, IMessage message), IMessage>((2, new IMessage.NoResult()));

.Deconstructor reads values as an enumerable.

IMessage oneOf = new IMessage.Error();
(int tag, IMessage msg) = accessor.Deconstructor.ReadAs<IMessage, (int tag, IMessage message)>(oneOf);

.Fields contains one-of option types.

IMessage oneOf = null!;
accessor.Fields[1].Writer.WriteAs<IMessage.Error, IMessage>(new IMessage.Error(), ref oneOf);
IMessage.Error result = accessor.Fields[1].Reader.ReadAs<IMessage, IMessage.Error>(oneOf);

.IsAssigned tests whether a oneof is assigned in container.

IMessage oneOf = new IMessage.Result();
bool nonNull = accessor.IsAssigned.Read(oneOf);

.Unassign removes oneof at container.

IMessage oneOf = new IMessage.Result();
accessor.Unassign.Write(default, ref oneOf);

Full Example

Full example

using Avalanche.Accessor;
using Avalanche.DataType;
using Avalanche.Service;
using Avalanche.Utilities;
using Avalanche.Writer;
using Microsoft.Extensions.DependencyInjection;
using static System.Console;

public class oneofattribute
{
    public static void Run()
    {
        {
            // <10>
            // Create service
            IService service = Services.Create(NetAccessorHandlers.Instance);
            // Create container target
            IContainerTarget target = new NetOneOf(typeof(IMessage));
            // Create request
            IRequestFor<IAccessor> request = new AccessorRequest(target);
            // Issue request
            IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);
            // </10>
        }
        {
            // <11>
            // Create service
            IService service = Services.Create(NetAccessorHandlers.Instance);
            // Create container target
            IContainerTarget target = new NetOneOf(typeof(IMessage));
            // Create request
            IRequestFor<IOneOfAccessor> request = new OneOfAccessorRequest(target);
            // Issue request
            IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);
            // </11>
        }
        {
            // <11B>
            // Create service
            IService service = Services.Create(NetAccessorHandlers.Instance);
            // Create container target
            IContainerTarget target = new NetOneOf(typeof(IMessage), typeof(object));
            // Create request
            IRequestFor<IOneOfAccessor> request = new OneOfAccessorRequest(target);
            // Issue request
            IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage, object>>(request);
            // </11B>
        }
        {
            // <12>
            // Create service
            IService service = Services.Create(NetAccessorHandlers.Instance);
            // Create container target
            IContainerTarget target = new NetOneOf(typeof(IMessage));
            // Create request
            IRequestFor<IOneOfAccessor> request = new OneOfAccessorRequest
            {
                Constructor = new ConstructorRequest(target),
                Deconstructor = new DeconstructorRequest(target),
                DefaultConstructor = new DefaultConstructorRequest(target),
                Fields = new ContentAccessorsRequest(target),
                IsAssigned = new IsAssignedRequest(target),
                Unassign = new UnassignRequest(target),
                ContainerType = new ContainerTypeRequest(target),
                ContentType = new ContentTypeRequest(target),
            };
            // Issue request
            IOneOfAccessor<IMessage> accessor = service.GetRequired<IRequest, IOneOfAccessor<IMessage>>(request);
            // </12>
        }

        {
            IOneOfAccessor<IMessage> accessor = Services.Create(NetAccessorHandlers.Instance)
                .GetRequiredService<IOneOfAccessor<IMessage>>();
            {
                // <51>
                IMessage oneOf = accessor.DefaultConstructor.Read();
                // </51>
            }
            {
                // <52>
                IMessage oneOf = accessor.Constructor.ReadAs<(int tag, IMessage message), IMessage>((2, new IMessage.NoResult()));
                // </52>
            }
            {
                // <53>
                IMessage oneOf = new IMessage.Error();
                (int tag, IMessage msg) = accessor.Deconstructor.ReadAs<IMessage, (int tag, IMessage message)>(oneOf);
                // </53>
            }
            {
                // <54>
                IMessage oneOf = null!;
                accessor.Fields[1].Writer.WriteAs<IMessage.Error, IMessage>(new IMessage.Error(), ref oneOf);
                IMessage.Error result = accessor.Fields[1].Reader.ReadAs<IMessage, IMessage.Error>(oneOf);
                // </54>
            }
            {
                // <62>
                IMessage oneOf = new IMessage.Result();
                bool nonNull = accessor.IsAssigned.Read(oneOf);
                // </62>
            }
            {
                // <63>
                IMessage oneOf = new IMessage.Result();
                accessor.Unassign.Write(default, ref oneOf);
                // </63>
            }
        }
    }

    // <100>
    [OneOf(typeof(Result), typeof(Error), typeof(NoResult))]
    public interface IMessage
    {
        public sealed class Result : IMessage { }
        public sealed class Error : IMessage { }
        public sealed class NoResult : IMessage { }
    }
    // </100>

}