This library provides a simple Optional (a.k.a. “Maybe”) type for C#. It allows you to express the presence or absence of a value without resorting to null. If an Optional<T> has a value, you can safely work with that value; if it doesn’t, the library’s methods help gracefully handle the “no value” scenario.
Why Use an Optional Type?
Clarity: Instead of passing null or returning null, an Optional<T> signals explicitly that the result might be absent.
Safety: Avoid NullReferenceException by forcing the developer to deal with the possibility of an empty value.
// Throws an ArgumentNullException if `value` is null
var maybeTen = Optional<int>.Of(10);
// Allows null but returns an empty Optional
var maybeName = Optional<string>.OfNullable(userName);
// A straightforward empty Optional
var none = Optional<int>.Empty();
Unboxing an optional
This is a simple and wrong way of unboxing an optional:
var maybeName = Optional<string>.OfNullable(userName);
if (maybeName.IsPresent())
{
var name = maybeName.Get();
}
While possible, this is not the suggested workflow, as it would be a glorified, more verbose null-check.
Instead...
Unboxing with fallback or error handling
var maybeName = Optional<string>.OfNullable(userName);
// Simple fallback
var name = maybeName.OrElse("No name provided");
// In case the fallback is expensive to compute
var name2 = maybeName.OrElseGet(() => GenerateRandomName());
// In case no fallback is possible
var name3 = empty.OrElseThrow(() => new Exception("Name is required"));
Filtering and mapping
It is possible to apply a Where clause to an Optional, returning empty if the predicate fails.
The content of an optional can then be transformed using the Select method, before being boxed back into an Optional.
This allows for a fluent, style of programming where the presence of the content is not required for the operations on it to take place.
var maybeUniverse = Optional<Universe>.Of(new Universe()
{
Age = 13.8
AgeUnit = "billion years"
});
var age = maybeUniverse
.Where(u => u.AgeUnit == "billion years")
.Whre(u => u.Age > 13)
.Select(u => u.Age)
.OrElseThrow(() => new Exception("No universe found"));
Conditional Actions
The IfPresent and IfNotPresent methods allow you to execute an action if the Optional has a value or not, respectively.
var maybeTen = Optional<int>.Of(10);
maybeTen
.IfPresent(value => Console.WriteLine($"The value is {value}"))
.OrElse(() => Console.WriteLine("No value"));
Collections
A version of FirstOrDefault that returns an Optional instead of null.
var fibonacci = new List<int>() = { 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 };
var firstEven = fibonacci
.FirstIfExists(optional => optional.Where(value => value % 2 == 0))
.OrElse(0);
Strings
var inputName = ReadInputName();
var name = inputName
.IfAny()
.OrElse("No name provided");
License
TinyOptional is licensed under the GPL v3. By using or redistributing this library, you agree to comply with the terms of that license.
