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effect

Struct overview

This module provides utility functions for working with structs in TypeScript.

Added in v2.0.0

Table of contents

combinators

getEquivalence

Given a struct of Equivalences returns a new Equivalence that compares values of a struct by applying each Equivalence to the corresponding property of the struct.

Alias of {@link Equivalence.struct}.

Signature

export declare const getEquivalence: <R extends Record<string, Equivalence.Equivalence<any>>>(
  isEquivalents: R
) => Equivalence.Equivalence<{ readonly [K in keyof R]: [R[K]] extends [Equivalence.Equivalence<infer A>] ? A : never }>

Example

import { Struct, String, Number } from "effect"

const PersonEquivalence = Struct.getEquivalence({
  name: String.Equivalence,
  age: Number.Equivalence
})

assert.deepStrictEqual(PersonEquivalence({ name: "John", age: 25 }, { name: "John", age: 25 }), true)
assert.deepStrictEqual(PersonEquivalence({ name: "John", age: 25 }, { name: "John", age: 40 }), false)

Added in v2.0.0

getOrder

This function creates and returns a new Order for a struct of values based on the given Orders for each property in the struct.

Alias of {@link order.struct}.

Signature

export declare const getOrder: <R extends { readonly [x: string]: order.Order<any> }>(
  fields: R
) => order.Order<{ [K in keyof R]: [R[K]] extends [order.Order<infer A>] ? A : never }>

Added in v2.0.0

utils

evolve

Transforms the values of a Struct provided a transformation function for each key. If no transformation function is provided for a key, it will return the origional value for that key.

Signature

export declare const evolve: {
  <O, T>(t: PartialTransform<O, T>): (obj: O) => Transformed<O, T>
  <O, T>(obj: O, t: PartialTransform<O, T>): Transformed<O, T>
}

Example

import { pipe, Struct } from "effect"

assert.deepStrictEqual(
  pipe(
    { a: "a", b: 1, c: 3 },
    Struct.evolve({
      a: (a) => a.length,
      b: (b) => b * 2
    })
  ),
  { a: 1, b: 2, c: 3 }
)

Added in v2.0.0

get

Retrieves the value associated with the specified key from a struct.

Signature

export declare const get: <K extends PropertyKey>(
  key: K
) => <S extends { [P in K]?: any }>(s: S) => MatchRecord<S, S[K] | undefined, S[K]>

Example

import { pipe, Struct } from "effect"

const value = pipe({ a: 1, b: 2 }, Struct.get("a"))

assert.deepStrictEqual(value, 1)

Added in v2.0.0

keys

Retrieves the object keys that are strings in a typed manner

Signature

export declare const keys: <T extends {}>(o: T) => Array<keyof T & string>

Example

import { Struct } from "effect"

const symbol: unique symbol = Symbol()

const value = {
  a: 1,
  b: 2,
  [symbol]: 3
}

const keys: Array<"a" | "b"> = Struct.keys(value)

assert.deepStrictEqual(keys, ["a", "b"])

Added in v3.6.0

omit

Create a new object by omitting properties of an existing object.

Signature

export declare const omit: {
  <Keys extends Array<PropertyKey>>(
    ...keys: Keys
  ): <S extends { [K in Keys[number]]?: any }>(s: S) => Simplify<Omit<S, Keys[number]>>
  <S extends object, Keys extends Array<keyof S>>(s: S, ...keys: Keys): Simplify<Omit<S, Keys[number]>>
}

Example

import { pipe, Struct } from "effect"

assert.deepStrictEqual(pipe({ a: "a", b: 1, c: true }, Struct.omit("c")), { a: "a", b: 1 })
assert.deepStrictEqual(Struct.omit({ a: "a", b: 1, c: true }, "c"), { a: "a", b: 1 })

Added in v2.0.0

pick

Create a new object by picking properties of an existing object.

Signature

export declare const pick: {
  <Keys extends Array<PropertyKey>>(
    ...keys: Keys
  ): <S extends { [K in Keys[number]]?: any }>(
    s: S
  ) => MatchRecord<S, { [K in Keys[number]]?: S[K] }, Simplify<Pick<S, Keys[number]>>>
  <S extends object, Keys extends Array<keyof S>>(
    s: S,
    ...keys: Keys
  ): MatchRecord<S, { [K in Keys[number]]?: S[K] }, Simplify<Pick<S, Keys[number]>>>
}

Example

import { pipe, Struct } from "effect"

assert.deepStrictEqual(pipe({ a: "a", b: 1, c: true }, Struct.pick("a", "b")), { a: "a", b: 1 })
assert.deepStrictEqual(Struct.pick({ a: "a", b: 1, c: true }, "a", "b"), { a: "a", b: 1 })

Added in v2.0.0