typescript optics
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
type Lens<State, Value> = { | |
(_: State): Value | |
set: (_: Value) => (_: State) => State | |
map<T>(_: Lens<Value, T>): Lens<State, T> | |
} | |
type Prop<K extends string, V = any> = Lens<Record<K, V>, V> | |
const prop = <K extends string, V>(key: K, defaultVal?: V): Prop<K, V> => { | |
const get = (obj: any) => obj[key] || defaultVal | |
const set = (val: any) => (obj: any) => ({ ...obj, [key]: val }) | |
return lens(get, set) as any | |
} | |
const lens = <S, T>( | |
get: (obj: S) => T, | |
set: (val: T) => (_: S) => S | |
): Lens<S, T> => { | |
const lens1 = (obj: S) => get(obj) | |
return Object.assign(lens1, { set, map: | |
<V extends any>(lens2: Lens<T, V>) => composeLenses(lens1 as any, lens2) | |
}) | |
} | |
const lensMap = <P extends string[]>(...props: P): { | |
[K in P[number]]: Prop<K> | |
} => Array<any>({}, ...props).reduce( | |
(map, key) => ({ ...map, [key]: prop(key, {}) }) | |
) | |
const composeLenses = <X, Y, Z>(lens1: Lens<X, Y>, lens2: Lens<Y, Z>): Lens<X, Z> => { | |
const get = (obj: X) => lens2(lens1(obj)) | |
const set = (val: Z) => (obj: X) => lens1.set(lens2.set(val)(lens1(obj)))(obj) | |
return lens(get, set) as any | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment