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import { computed, untracked } from '@angular/core'
import type { Signal } from '@angular/core'
export type MapToSignals<T> = {
[K in keyof T]: T[K] extends Function ? T[K] : Signal<T[K]>
}
/**
* Exposes fields of an object passed via an Angular `Signal` as `Computed` signals.
* Functions on the object are passed through as-is.
* @param inputSignal - `Signal` that must return an object.
* @returns A proxy object with the same fields as the input object, but with each field wrapped in a `Computed` signal.
*/
export function signalProxy<TInput extends Record<string | symbol, any>>(
inputSignal: Signal<TInput>,
) {
const internalState = {} as MapToSignals<TInput>
return new Proxy<MapToSignals<TInput>>(internalState, {
get(target, prop) {
// first check if we have it in our internal state and return it
const computedField = target[prop]
if (computedField) return computedField
// then, check if it's a function on the resultState and return it
const targetField = untracked(inputSignal)[prop]
if (typeof targetField === 'function') return targetField
// finally, create a computed field, store it and return it
// @ts-expect-error
return (target[prop] = computed(() => inputSignal()[prop]))
},
has(_, prop) {
return !!untracked(inputSignal)[prop]
},
ownKeys() {
return Reflect.ownKeys(untracked(inputSignal))
},
getOwnPropertyDescriptor() {
return {
enumerable: true,
configurable: true,
}
},
})
}
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