0.0.4 • Published 3 years ago
pattern-match-ts v0.0.4
Index
Installation
yarn
yarn add pattern-matching-tsnpm
npm install --save pattern-matching-tsUsage
MatchW
Option MatchW
import * as M from 'pattern-matching-ts/lib/match'
import { pipe } from 'fp-ts/lib/function'
import * as O from 'fp-ts/lib/Option'
const optionMatching = (o: unknown) =>
pipe(
o,
M.matchW('_tag')({
Some: ({ value }) => 'Something: ' + value,
None: () => 'Nothing',
_: () => 'Default'
})
)
assert.deepStrictEqual(optionMatching(O.some('data')), 'Something: data')
assert.deepStrictEqual(optionMatching(O.none), 'Nothing')
assert.deepStrictEqual(optionMatching((undefined as unknown) as O.None), 'Default')Either MatchW
import * as M from 'pattern-matching-ts/lib/match'
import { pipe } from 'fp-ts/lib/function'
import * as E from 'fp-ts/lib/Either'
type RGB = Record<'r' | 'g' | 'b', number>
const either = (maybeRgb: E.Either<string, RGB>) =>
pipe(
maybeRgb,
M.matchW('_tag')({
Left: ({ left }) => 'Error: ' + left,
Right: ({ right: { r, g, b } }) => `Red: ${r} | Green: ${g} | Blue: ${b}`
})
)
assert.deepStrictEqual(either(E.right({ r: 255, g: 255, b: 0 })), 'Red: 255 | Green: 255 | Blue: 0')Default MatchW
import * as M from 'pattern-matching-ts/lib/match'
import { pipe } from 'fp-ts/lib/function'
interface ServerResponse<Code extends string | number> {
readonly code: Code
}
interface Response<Body> {
readonly response: {
readonly body: Body
}
}
interface Success extends ServerResponse<200>, Response<ReadonlyArray<string>> {}
interface NotFoundError extends ServerResponse<404> {}
interface ServerError extends ServerResponse<500> {
readonly detail: string
}
type Responses = Success | NotFoundError | ServerError
const matchResponse = (response: Responses) =>
pipe(
response,
M.matchW('code')({
500: ({ detail }) => ({ message: 'Internal server error', detail }),
404: () => ({ message: 'The page cannot be found!' }),
200: ({ response }) => response.body,
_: () => 'Unexpected response'
})
)
assert.deepStrictEqual(either(E.right({ r: 255, g: 255, b: 0 })), 'Red: 255 | Green: 255 | Blue: 0')
assert.deepStrictEqual(matchResponse({ code: 200, response: { body: ['data'] } }), ['data'])
assert.deepStrictEqual(matchResponse({ code: 500, detail: 'Cannot connect to the database' }), {
message: 'Internal server error',
detail: 'Cannot connect to the database'
})
assert.deepStrictEqual(matchResponse({ code: 404 }), { message: 'The page cannot be found!' })Match
Option Match
import * as M from 'pattern-matching-ts/lib/match'
import * as O from 'fp-ts/lib/Option'
const optionMatching = M.match<O.Option<string>, string>({
Some: (x) => `Something: ${x.value}`,
None: () => 'Nothing'
})
assert.deepStrictEqual(optionMatching(O.some('data')), 'Something: data')
assert.deepStrictEqual(optionMatching(O.none), 'Nothing')Default Match
import * as M from 'pattern-matching-ts/lib/match'
interface ChangeColor<T = number> {
readonly _tag: 'ChangeColor'
readonly value: {
readonly r: T
readonly g: T
readonly b: T
}
}
interface Move<T = number> {
readonly _tag: 'Move'
readonly value: {
readonly x: T
readonly y: T
}
}
interface Write {
readonly _tag: 'Write'
readonly value: {
readonly text: string
}
}
type Cases = ChangeColor<number> | Move | Write
const matchMessage = M.match<Cases, string>({
ChangeColor: ({ value: { r, g, b } }) => `Change the color to Red: ${r} | Green: ${g} | Blue: ${b}`,
Move: ({ value: { x, y } }) => `Move in the x direction: ${x} and in the y direction: ${y}`,
Write: ({ value: { text } }) => `Text message: ${text}`,
_: () => 'Default message'
})
const ChangeColor = ({ r, g, b }: ChangeColor<number>['value']): ChangeColor<number> => ({
_tag: 'ChangeColor',
value: { r, g, b }
})
const Move = ({ x, y }: Move['value']): Move => ({
_tag: 'Move',
value: { x, y }
})
const Write = ({ text }: Write['value']): Write => ({
_tag: 'Write',
value: { text }
})
assert.deepStrictEqual(
matchMessage(Move({ x: 500, y: 100 })),
'Move in the x direction: 500 and in the y direction: 100'
)
assert.deepStrictEqual(
matchMessage(ChangeColor({ r: 12, g: 20, b: 30 })),
'Change the color to Red: 12 | Green: 20 | Blue: 30'
)
assert.deepStrictEqual(matchMessage(Write({ text: 'my message' })), 'Text message: my message')Blog posts that introduces the API.
👉 Pattern Matching in Typescript