public static MaybeNotNull <K> SelectMany <T, K>(this MaybeNotNull <T> source, Func <T, K> maybeSelector)
{
//Contract.Requires( source != null );
//Contract.Requires( maybeSelector != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<K>>() != null );
return(source.SelectMany(maybeSelector, (_, x) => x));
}
public static MaybeNotNull <R> SelectMany <T, K, R>(this MaybeNotNull <T> source, Func <T, K> maybeSelector, Func <T, K, R> resultSelector)
{
//Contract.Requires( source != null );
//Contract.Requires( maybeSelector != null );
//Contract.Requires( resultSelector != null );
return(source.SelectMany(t => Value(maybeSelector(t)), resultSelector));
}
public static MaybeNotNull <T> Catch <T, TException>(this MaybeNotNull <T> source, Func <TException, T> getValue)
where TException : Exception
{
//Contract.Requires( source != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<T>>() != null );
return(source.Catch((TException ex) => Maybe.Value(getValue(ex))));
}
public static MaybeNotNull <T> Catch <T>(this MaybeNotNull <T> source, MaybeNotNull <T> defaultValue)
{
//Contract.Requires( source != null );
//Contract.Requires( defaultValue != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<T>>() != null );
return(source.Kind == MaybeKind.Error ? defaultValue : source);
}
public static MaybeNotNull <T> Where <T>(this MaybeNotNull <T> source, Func <T, bool> predicate)
{
//Contract.Requires( source != null );
//Contract.Requires( predicate != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<T>>() != null );
return(from t in source
from _ in predicate(t) ? "" : null
select t);
}
public static OpResult Lift(this MaybeNotNull <OpResult> maybe, OpResult nullResult = null)
{
//Contract.Requires( maybe != null );
//Contract.Ensures( //Contract.Result<OpResult>() != null );
return
(maybe.Kind == MaybeKind.Error ? OpResult.FromException(maybe.Exception) :
(maybe.ValueOrNull() ?? nullResult ?? OpResult.Failed("Unknown error has occurred")));
}
public static MaybeNotNull <T> OrMaybe <T>(this MaybeNotNull <T> source, Func <MaybeNotNull <T> > whenNull)
{
//Contract.Requires( source != null );
//Contract.Requires( whenNull != null );
if (source.Kind == MaybeKind.Null)
{
return(whenNull());
}
return(source);
}
public static MaybeNotNull <T> Catch <T, TException>(this MaybeNotNull <T> source, Func <TException, MaybeNotNull <T> > getValue)
where TException : Exception
{
//Contract.Requires( source != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<T>>() != null );
if (source.Kind == MaybeKind.Error)
{
var e = source.Exception as TException;
if (e != null)
{
return(getValue(e));
}
}
return(source);
}
public override MaybeNotNull <R> SelectMany <K, R>(Func <T, MaybeNotNull <K> > maybeSelector, Func <T, K, R> resultSelector)
{
try
{
var k = maybeSelector(this.Value);
if (k.Kind == MaybeKind.Value)
{
var res = resultSelector(this.Value, k.Value);
return(isNull(res) ? MaybeNotNull <R> .MakeNull() : MaybeNotNull <R> .MakeValue(res));
}
else
{
return(k.SelectMany <R, R>(null, null));
}
}
catch (Exception ex)
{
return(MaybeNotNull <R> .MakeError(ex));
}
}
public static T ValueOrDefault <T>(this MaybeNotNull <T> maybe, T defaultValue)
{
//Contract.Requires( maybe != null );
return(maybe.Kind == MaybeKind.Null ? defaultValue : maybe.Value);
}
public static MaybeNotNull <T> Or <T>(this MaybeNotNull <T> source, Func <T> whenNull)
{
//Contract.Requires( source != null );
//Contract.Requires( whenNull != null );
return(source.OrMaybe(() => Maybe.Value(whenNull())));
}
public static MaybeNotNull <T> Value <T>(T value)
{
return(value == null?Null <T>() : MaybeNotNull <T> .MakeValue(value));
}
public static T?AsNullable <T>(this MaybeNotNull <T?> source) where T : struct
{
//Contract.Requires( source != null );
return(source.Kind == MaybeKind.Null ? new T?() : source.Value);
}
public static MaybeNotNull <T> Throw <T>(Exception ex)
{
return(MaybeNotNull <T> .MakeError(ex));
}
public static MaybeNotNull <T> Do <T>(this MaybeNotNull <T> source, Action <T> a)
{
//Contract.Requires( source != null );
//Contract.Requires( a != null );
return(source.Select(x => { a(x); return x; }));
}
public static MaybeNotNull <T> Catch <T>(this MaybeNotNull <T> source, T defaultValue)
{
//Contract.Requires( source != null );
//Contract.Ensures( //Contract.Result<MaybeNotNull<T>>() != null );
return(source.Catch(Maybe.Value(defaultValue)));
}
public static T?ValueOrNull <T>(this MaybeNotNull <T?> maybe) where T : struct
{
//Contract.Requires( maybe != null );
return(maybe.Kind == MaybeKind.Null ? null : maybe.Value);
}
public static T ValueOrDefault <T>(this MaybeNotNull <T> maybe) where T : struct
{
//Contract.Requires( maybe != null );
return(maybe.Kind == MaybeKind.Null ? default(T) : maybe.Value);
}
public static MaybeNotNull <T> Null <T>()
{
return(MaybeNotNull <T> .MakeNull());
}