effect-io-ai

Package: effect
Module: TxHashMap

TxHashMap.modifyAt

Updates the value for the specified key using an Option-based update function.

Details

This function mutates the original TxHashMap by updating, adding, or removing the key-value pair based on the function result. It does not return a new TxHashMap reference.

Example (Updating values with Option)

import { Effect, TxHashMap } from "effect"

const program = Effect.gen(function*() {
  const storage = yield* TxHashMap.make<string, string | number>([
    "file1.txt",
    "content1"
  ], ["access_count", 0])

  // Increment existing counter
  yield* TxHashMap.modifyAt(storage, "access_count", (current) =>
    current._tag === "Some" && typeof current.value === "number"
      ? { ...current, value: current.value + 1 }
      : current
  )
  const count1 = yield* TxHashMap.get(storage, "access_count")
  console.log(count1) // Option.some(1)

  // Increment existing counter again
  yield* TxHashMap.modifyAt(storage, "access_count", (current) =>
    current._tag === "Some" && typeof current.value === "number"
      ? { ...current, value: current.value + 1 }
      : current
  )
  const count2 = yield* TxHashMap.get(storage, "access_count")
  console.log(count2) // Option.some(2)

  // Update an existing string entry
  yield* TxHashMap.modifyAt(storage, "file1.txt", (current) =>
    current._tag === "Some" && typeof current.value === "string"
      ? { ...current, value: `${current.value}.bak` }
      : current
  )
  const backup = yield* TxHashMap.get(storage, "file1.txt")
  console.log(backup) // Option.some("content1.bak")
})

Signature

declare const modifyAt: { <K, V>(key: K, f: (value: Option.Option<V>) => Option.Option<V>): (self: TxHashMap<K, V>) => Effect.Effect<void>; <K, V>(self: TxHashMap<K, V>, key: K, f: (value: Option.Option<V>) => Option.Option<V>): Effect.Effect<void>; }

Source

Since v4.0.0