Core APIEnum methods

Enum methods

matches

matches<K>(variant: K): this is EnumNarrowed<this, V, K>

Returns true if the variant is passed variant.

PropTypeDefault
variant
K
-
import { Ok, Err } from "tnum/std";

const res = Ok(200);

// short version of this code is `res.isOk()`.
if (res.matches("Ok")) {
  res.takeVariantValue(); // result-type is number.
}

match

match<T>(arms: EnumMatchArms<V, T>): Exclude<T, never>

This method is alternative of match expression. You can catch variant and containig value by arm(type: [variant-name](value): T). _ arm catches uncaught variants. You must write arms so that it catches all variants. This method returns the return value of arm that caught the variant.

PropTypeDefault
arms
EnumMatchArms<V, T>
-
import { Some } from "tnum/std";

const optName = Some("hoge");

// short version of this code is `optName.unwrapOr("[no name]");`.
const name: string = optName.match({
  Some: (name) => name,
  _: () => "[no name]",
});

getVariant

getVariant(): K

Returns the variant string.

import { Some, None } from "tnum/std";

const some = Some(1024);
const none = None();

console.log(some.getVariant()); // "Some"
console.log(none.getVariant()); // "None"

takeVariantValue

takeVariantValue(): NV

Returns the variant value. The return value type is narrowed by current K.

import { Some, None } from "tnum/std";

const some = Some(1024);
const none = None();

console.log(some.takeVariantValue()); // 1024
console.log(none.takeVariantValue()); // null

some.takeVariantValue(); // → number | null

if (some.isSome()) {
  // narrowed by isSome()
  some.takeVariantValue(); // → number
}

toJSON

toJSON(): string

Returns JSON representation.

import { Some, None } from "tnum/std";

const opt = Some(1024);
console.log(opt.toJSON()); // "{"variant":"Some","value":1024}"

Enum generics

Standard enums

On this page

matchesmatchgetVarianttakeVariantValuetoJSON