Struct

Option<T>

union struct Option<T>

Namespace: System
Assembly: Raven.Core.dll
Source file: Option.rvn

Inheritance: object → ValueType → Option<T>
Implements: IPropagatable<Option<T>, T, ()>

Represents some value, or no value.

Usage

Use Option like so:

func Test(v: int) -> Option<int> {
    if v > 3 {
        return Some(42)
    }
    None
}

Matching result in match expression:

let result = Test(2)

let r = result match {
    Some(let value) => "Some: $value"
    None => "None"
}

Simple pattern:

if result is Some(let value) {
    // Omitted
} else if result is None {
    // Omitted
}

Type parameters

Name	Description
`T`	The type of the optional value.

Cases

2 cases

case Some(value: T) Represents an available value.

case None Represents the absence of a value.

Properties

4 items

val HasNone: bool Gets a value indicating whether this option is `None`. val HasSome: bool Gets a value indicating whether this option is `Some`. val HasValue: bool Represents some value, or no value. val Value: object? Represents some value, or no value.

Methods

23 items

func Filter(predicate: T -> bool) -> Option<T> Alias for `Where`. static func FromResidual(residual: ()) -> Option<T> Constructs an empty option from a propagated residual. func GetEnumerator() -> IEnumerator<T> Returns an enumerator over the zero-or-one contained values. func Map<TResult>(mapper: T -> TResult) -> Option<TResult> Projects the value inside `Some` using `mapper`. `None` stays `None`. func MapResult<TResult, E>(mapper: T -> TResult, noneError: () -> E) -> Result<TResult, E> Maps the contained value into a `Result`. If this is `None`, returns `Error(noneError())`. func Match<TResult>(some: T -> TResult, none: () -> TResult) -> TResult Matches the option and produces a value. func OkOr<E>(error: E) -> Result<T, E> Converts this option into a result, using `error` when it is `None`. func OkOr<E>(errorFactory: () -> E) -> Result<T, E> Converts this option into a result, evaluating `errorFactory` when it is `None`. func OrElse(alternative: () -> Option<T>) -> Option<T> Returns this option if it is `Some`, otherwise returns `alternative()`. func Tap(action: T -> ()) -> Option<T> Runs `action` if this is `Some`, returning the original option. func TapNone(action: () -> ()) -> Option<T> Runs `action` if this is `None`, returning the original option. func Then<TResult>(binder: T -> Option<TResult>) -> Option<TResult> Monadic bind / flatMap: chains an `Option`-producing function. func ThenResult<TResult, E>(binder: T -> Result<TResult, E>, noneError: () -> E) -> Result<TResult, E> Bridges `Option` into a `Result`-producing pipeline. If this is `None`, returns `Error(noneError())`. func ToEnumerable() -> IEnumerable<T> Converts `Some(x)` to a single-item sequence and `None` to an empty sequence. virtual override func ToString() -> string No summary available. virtual override func ToString() -> string Represents some value, or no value. func TryGetOutput(out output: T) -> bool Attempts to extract the successful output used by the propagation protocol. func TryGetResidual(out residual: ()) -> bool Reports absence as the unit residual used by the propagation protocol. func UnwrapOr(defaultValue: T) -> T Returns the contained value, or `defaultValue` when this option is `None`. func UnwrapOrDefault() -> T Returns the contained value, or the default value when this option is `None`. func UnwrapOrElse(factory: () -> T) -> T Returns the contained value or evaluates `factory()`. func UnwrapOrThrow() -> T Returns the contained value, or throws when this option is `None`. func Where(predicate: T -> bool) -> Option<T> Keeps the value only if `predicate` returns true.