Resolve

Extracts the final TReturn result from the train. Used in the RunInternal path as the last method call. Follows a priority chain: exception > short-circuit value > Memory lookup.

Note: When using Junctions(), resolution happens automatically via an implicit conversion and you do not call Resolve yourself. This method is only needed when overriding RunInternal.

Signatures

Resolve()

Extracts the result from Memory (or exception/short-circuit).

public Either<Exception, TReturn> Resolve()

Resolve(Either<Exception, TReturn> returnType)

Returns an explicit result (or the exception if one exists).

public Either<Exception, TReturn> Resolve(Either<Exception, TReturn> returnType)

Parameter	Type	Description
returnType	Either<Exception, TReturn>	An explicit Either result. Only used if the train has no exception.

Returns

Either<Exception, TReturn>, the train result. Left contains the exception on failure; Right contains the TReturn value on success.

Examples

Standard Usage (RunInternal path)

protected override async Task<Either<Exception, OrderResult>> RunInternal(OrderInput input) =>
    Activate(input)
        .Chain<ValidateOrder>()
        .Chain<ProcessPayment>()     // Stores OrderResult in Memory
        .Resolve();                  // Extracts OrderResult from Memory

With Explicit Result

protected override async Task<Either<Exception, string>> RunInternal(Unit input)
{
    Either<Exception, string> result = "hello";
    return Activate(input)
        .Resolve(result);    // Returns "hello" (unless an exception occurred)
}

Resolution Priority

Resolve() follows this order:

1. Exception: If any junction set an exception, return Left(exception).
2. Short-circuit value: If ShortCircuit captured a value, return Right(shortCircuitValue).
3. Memory lookup: Extract TReturn from Memory by type.
4. Fallback: If TReturn is not found in Memory, return Left(TrainException("Could not find type: ({TReturn}).")).

Remarks

• Resolve() does not throw. It returns an Either. The calling Run() method unwraps the Either and throws if needed.
• The parameterized Resolve(returnType) is simpler: it returns the exception if one exists, otherwise returns the provided value. It does not check short-circuit or Memory.