/// <summary>
/// Converts a single result option to another option based on its contents.
/// </summary>
/// <remarks>
/// <para>
/// This method is implemented using deferred execution; the query represented by this method
/// is not performed until the contents of the returned option are resolved, such as by enumeration.
/// </para>
/// </remarks>
/// <typeparam name="TSource">The element type of <paramref name="source"/>.</typeparam>
/// <typeparam name="TResult">The element type of the result option for this conversion.</typeparam>
/// <param name="source">A source single result option.</param>
/// <param name="ifZero">
/// A function to produce the result if <paramref name="source"/> represents a result of zero elements.
/// </param>
/// <param name="ifOne">
/// A function to produce the result if <paramref name="source"/> represents a result of one
/// element, which accepts that element as a parameter.
/// </param>
/// <param name="ifMoreThanOne">
/// A function to produce the result if <paramref name="source"/> represents a result of more
/// than one element.
/// </param>
/// <returns>
/// An option equivalent to the result of calling <paramref name="ifZero"/>, <paramref
/// name="ifOne"/>, or <paramref name="ifMoreThanOne"/> if <paramref name="source"/>
/// represents a result of zero, one, or more than one element, respectively.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="InvalidOperationException">
/// <paramref name="ifZero"/> is <see langword="null"/> and <paramref name="source"/>
/// represents a result of zero elements, or <paramref name="ifOne"/> is <see
/// langword="null"/> and <paramref name="source"/> represents a result of one element, or
/// <paramref name="ifMoreThanOne"/> is <see langword="null"/> and <paramref name="source"/>
/// represents a result of more than one element.
/// </exception>
public static IOpt <TResult> MatchOpt <TSource, TResult>(this ISingleResultOpt <TSource> source, Func <Opt <TResult> > ifZero = null, Func <TSource, Opt <TResult> > ifOne = null, Func <Opt <TResult> > ifMoreThanOne = null)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
return(Opt.DeferRaw(() => source.Match(ifZero, ifOne, ifMoreThanOne)));
}
public Opt <T> ToFixed()
{
if (IsValidOption)
{
return(Opt.Create(HasValue, ValueOrDefault));
}
throw Error.MoreThanOneResult(UsingPredicate);
}
Opt <object> IOptFixable.ToFixed()
{
if (IsValidOption)
{
return(Opt.Create <object>(HasValue, ValueOrDefault));
}
throw Error.MoreThanOneResult(UsingPredicate);
}
/// <summary>
/// Converts a single result option to another option, substituting a specified option if
/// this option represents more than one result.
/// </summary>
/// <typeparam name="TSource">The element type of <paramref name="source"/>.</typeparam>
/// <param name="source">A source single result option.</param>
/// <param name="replacement">
/// An option to produce the result if <paramref name="source"/> represents a result of more
/// than one element.
/// </param>
/// <returns>
/// An option equivalent to <paramref name="source"/>, if it represents a result of zero or
/// one element; otherwise, an option equivalent to <paramref name="replacement"/>.
/// </returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="source"/> or <paramref name="replacement"/> is <see langword="null"/>.
/// </exception>
public static IOpt <TSource> ReplaceIfMoreThanOne <TSource>(this ISingleResultOpt <TSource> source, IOpt <TSource> replacement)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (replacement == null)
{
throw new ArgumentNullException(nameof(replacement));
}
return(Opt.DeferRaw(() => ReplaceIfMoreThanOneImmediate(source, replacement)));
}
/// <summary>
/// Converts a single result option to another option, substituting the result of a callback
/// if this option represents more than one result.
/// </summary>
/// <typeparam name="TSource">The element type of <paramref name="source"/>.</typeparam>
/// <param name="source">A source single result option.</param>
/// <param name="replacementFactory">
/// A function to produce the result if <paramref name="source"/> represents a result of more
/// than one element.
/// </param>
/// <returns>
/// An option equivalent to <paramref name="source"/>, if it represents a result of zero or
/// one element; otherwise, an option equivalent to the result of calling <paramref name="replacementFactory"/>.
/// </returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="source"/> or <paramref name="replacementFactory"/> is <see langword="null"/>.
/// </exception>
public static IOpt <TSource> ReplaceIfMoreThanOne <TSource>(this ISingleResultOpt <TSource> source, Func <IOpt <TSource> > replacementFactory)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (replacementFactory == null)
{
throw new ArgumentNullException(nameof(replacementFactory));
}
return(Opt.DeferRaw(() => ReplaceIfMoreThanOneImmediate(source, Opt.DeferRaw(() => Opt.Fix(replacementFactory())))));
}
public bool MoveNext()
{
if (isResolved)
{
return(false);
}
else
{
var fixedSource = Opt.Fix(source);
var moved = fixedSource.HasValue;
Current = fixedSource.ValueOrDefault;
isResolved = true;
return(moved);
}
}
/// <summary> /// Converts a single result option to another option, substituting an empty option if this /// option represents more than one result. /// </summary> /// <typeparam name="TSource">The element type of <paramref name="source"/>.</typeparam> /// <param name="source">A source single result option.</param> /// <returns> /// An option equivalent to <paramref name="source"/>, if it represents a result of zero or /// one element; otherwise, an empty option. /// </returns> /// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception> public static IOpt <TSource> EmptyIfMoreThanOne <TSource>(this ISingleResultOpt <TSource> source) => source.ReplaceIfMoreThanOne(Opt.Empty <TSource>());
/// <summary> /// Converts a single result option to another option, substituting a full option containing /// the specified default value if this option represents more than one result. /// </summary> /// <typeparam name="TSource">The element type of <paramref name="source"/>.</typeparam> /// <param name="source">A source single result option.</param> /// <param name="defaultValue"> /// The value to be contained by the returned option if <paramref name="source"/> represents /// more than one result. /// </param> /// <returns> /// An option equivalent to <paramref name="source"/>, if it represents a result of zero or /// one element; otherwise, an option containing <paramref name="defaultValue"/>. /// </returns> /// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception> public static IOpt <TSource> DefaultIfMoreThanOne <TSource>(this ISingleResultOpt <TSource> source, TSource defaultValue) => source.ReplaceIfMoreThanOne(Opt.Full <TSource>(defaultValue));
internal static FixedSingleResultOpt <TSource> GetFixedFromOpt <TSource>(Opt <TSource> source, bool usingPredicate) => GetFixedFromValue(source.HasValue, source.ValueOrDefault, usingPredicate);
public override Opt <T> ToFixed() => metaselector(Opt.Fix(source));
