osu/osu.Game/Utils/Optional.cs

43 lines
1.4 KiB
C#

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
namespace osu.Game.Utils
{
/// <summary>
/// A wrapper over a value and a boolean denoting whether the value is valid.
/// </summary>
/// <typeparam name="T">The type of value stored.</typeparam>
public readonly ref struct Optional<T>
{
/// <summary>
/// The stored value.
/// </summary>
public readonly T Value;
/// <summary>
/// Whether <see cref="Value"/> is valid.
/// </summary>
/// <remarks>
/// If <typeparamref name="T"/> is a reference type, <c>null</c> may be valid for <see cref="Value"/>.
/// </remarks>
public readonly bool HasValue;
private Optional(T value)
{
Value = value;
HasValue = true;
}
/// <summary>
/// Returns <see cref="Value"/> if it's valid, or a given fallback value otherwise.
/// </summary>
/// <remarks>
/// Shortcase for: <c>optional.HasValue ? optional.Value : fallback</c>.
/// </remarks>
/// <param name="fallback">The fallback value to return if <see cref="HasValue"/> is <c>false</c>.</param>
public T GetOr(T fallback) => HasValue ? Value : fallback;
public static implicit operator Optional<T>(T value) => new Optional<T>(value);
}
}