public static Maybe <T> TryLast <T>(this IEnumerable <T> source, Func <T, bool> predicate)
{
var last = source.LastOrDefault(predicate);
if (last != null)
{
return(Maybe <T> .From(last));
}
return(Maybe <T> .None);
}
public static Maybe <T> TryFirst <T>(this IEnumerable <T> source, Func <T, bool> predicate)
{
var firstOrEmpty = source.Where(predicate).Take(1).ToList();
if (firstOrEmpty.Any())
{
return(Maybe <T> .From(firstOrEmpty[0]));
}
return(Maybe <T> .None);
}
/// <summary>
/// Creates a new <see cref="Maybe{T}" /> if <paramref name="maybeTask" /> is empty, using the result of the supplied <paramref name="fallbackOperation" />, otherwise it returns <paramref name="maybeTask" />
/// </summary>
/// <param name="maybeTask"></param>
/// <param name="fallbackOperation"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static async Task <Maybe <T> > Or <T>(this Task <Maybe <T> > maybeTask, Func <T> fallbackOperation)
{
Maybe <T> maybe = await maybeTask.DefaultAwait();
if (maybe.HasNoValue)
{
return(Maybe <T> .From(fallbackOperation()));
}
return(maybe);
}
/// <summary>
/// Creates a new <see cref="Maybe{T}" /> if <paramref name="maybeTask" /> is empty, using the supplied <paramref name="fallback" />, otherwise it returns <paramref name="maybeTask" />
/// </summary>
/// <param name="maybeTask"></param>
/// <param name="fallback"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static async Task <Maybe <T> > Or <T>(this Task <Maybe <T> > maybeTask, Task <T> fallback)
{
Maybe <T> maybe = await maybeTask.DefaultAwait();
if (maybe.HasNoValue)
{
var value = await fallback.DefaultAwait();
return(Maybe <T> .From(value));
}
return(maybe);
}
/// <summary>
/// When bool value is true returns Result.Success otherwise Result.Fail
/// </summary>
/// <param name="val"></param>
/// <param name="error"></param>
/// <returns></returns>
public static Result ToResult(this bool val, string error)
{
return(Maybe <bool> .From(val).ToValidResult(error)
.OnSuccess(x => x ? Result.Success() : Result.Fail(error)));
}