Option (effect)

Combining

all

ap

product

productMany

Constructors

fromIterable

none

some

Conversions

<A>(nullableValue: A) => Option.Option<NonNullable<A>>

nullableをOptionに変換

code:ts

console.log(Option.fromNullable(undefined)) // None

console.log(Option.fromNullable(null)) // None

console.log(Option.fromNullable(1)) // Some(1)

Option → a

Someから値を取り出す

Noneならthrow

Either → Option

EirherがrightならSome

Either → Option

EirherがleftならSome

nullableな普通の関数を、Optionを返すような関数にlifting

(a -> a|null) -> a -> Option<a>

liftThrowable

code:ts

console.log(Option.toArray(Option.some(1)))

console.log(Option.toArray(Option.none()))

// Output: []

toRefinement

Do notation

Do

code:ts

import * as assert from "node:assert"

import { Option, pipe } from "effect"

const result = pipe(

Option.Do,

Option.bind("x", () => Option.some(2)),

Option.bind("y", () => Option.some(3)),

Option.let("sum", ({ x, y }) => x + y),

Option.filter(({ x, y }) => x * y > 5)

)

assert.deepStrictEqual(result, Option.some({ x: 2, y: 3, sum: 5 }))

bind

bindTo

let

Elements

contains

containsWith

exists

Equivalence

getEquivalence

Error handling

Filtering

普通の述語関数を引数に取る

述語がtrueのときにSomeを返す

<A>(predicate: Predicate<NoInfer<A>>): (self: Option<A>) => Option<A>

partitionMap

Generators

gen

Getters

Guards

isNone

isOption

isSome

Lifting

lift2

liftPredicate

Mapping

as

asVoid

Models

None (interface)

Option (type alias)

OptionUnify (interface)

OptionUnifyIgnore (interface)

Some (interface)

Pattern matching

match

Reducing

reduceCompact

Sequencing

2つのOptionをチェーンする

code:ts

const parse = (s: string): Option.Option<number> => (isNaN(Number(s)) ? Option.none() : Option.some(Number(s)))

const double = (n: number): Option.Option<number> => (n > 0 ? Option.some(n * 2) : Option.none())

// string → Option<number>

const parseAndDouble = Option.composeK(parse, double)

flatMapNullable

tap

Sorting

getOrder

Symbols

TypeId

TypeId (type alias)

Type Lambdas

OptionTypeLambda (interface)

Zipping

utils

Option (namespace)

Value (type alias)

void