/// <summary>
/// Combine three <see cref="Errorable{T}"/> values and return a result.
/// </summary>
/// <remarks>Any errors already present are preserved.</remarks>
/// <typeparam name="T">Type of value possibly present in <paramref name="first"/>.</typeparam>
/// <typeparam name="A">Type of value possibly present in <paramref name="second"/>.</typeparam>
/// <typeparam name="B">Type of value possibly present in <paramref name="third"/>.</typeparam>
/// <typeparam name="R">Type of return value.</typeparam>
/// <param name="first">First errorable value.</param>
/// <param name="second">Second errorable value.</param>
/// <param name="third">Third errorable value.</param>
/// <param name="combinerFunc">Function to combine all three values when available.</param>
/// <returns>An errorable containing either the result of combining both available values,
/// or a combined set of errors.</returns>
public static Errorable <R> Combine <T, A, B, R>(
this Errorable <T> first,
Errorable <A> second,
Errorable <B> third,
Func <T, A, B, R> combinerFunc)
{
if (first == null)
{
throw new ArgumentNullException(nameof(first));
}
if (second == null)
{
throw new ArgumentNullException(nameof(second));
}
if (third == null)
{
throw new ArgumentNullException(nameof(third));
}
if (combinerFunc == null)
{
throw new ArgumentNullException(nameof(combinerFunc));
}
if (first.HasValue && second.HasValue && third.HasValue)
{
return(Errorable.Success(
combinerFunc(first.Value, second.Value, third.Value)));
}
var allErrors = first.Errors.Union(second.Errors)
.Union(third.Errors);
return(Errorable.Failure <R>(allErrors));
}
/// <summary>
/// Combine two <see cref="Errorable{T}"/> values
/// </summary>
/// <typeparam name="T">Type of value possibly present in <paramref name="first"/>.</typeparam>
/// <typeparam name="A">Type of value possibly present in <paramref name="second"/>.</typeparam>
/// <param name="first">First errorable value.</param>
/// <param name="second">Second errorable value.</param>
/// <param name="whenSuccessful">Action to take when both values are available.</param>
/// <param name="whenFailure">Action to take if either (or both) errorables have errors.</param>
public static void Combine <T, A>(
this Errorable <T> first,
Errorable <A> second,
Action <T, A> whenSuccessful,
Action <IEnumerable <string> > whenFailure)
{
if (first == null)
{
throw new ArgumentNullException(nameof(first));
}
if (second == null)
{
throw new ArgumentNullException(nameof(second));
}
if (whenSuccessful == null)
{
throw new ArgumentNullException(nameof(whenSuccessful));
}
if (whenFailure == null)
{
throw new ArgumentNullException(nameof(whenFailure));
}
if (first.HasValue && second.HasValue)
{
whenSuccessful(first.Value, second.Value);
}
else
{
var allErrors = first.Errors.Union(second.Errors);
whenFailure(allErrors);
}
}
