effect-io-ai

Package: effect
Module: Effect

Effect.contextWith

Transforms the current context using the provided function.

When to use

Use to derive an effect from the complete Context.

Details

This function allows you to access the complete context and perform computations based on all available services. This is useful when you need to conditionally execute logic based on what services are available.

Example (Deriving values from the context)

import { Console, Context, Effect, Option } from "effect"

const Logger = Context.Service<{
  log: (msg: string) => void
}>("Logger")
const Cache = Context.Service<{
  get: (key: string) => string | null
}>("Cache")

const program = Effect.contextWith((services) => {
  const cacheOption = Context.getOption(services, Cache)
  const hasCache = Option.isSome(cacheOption)

  if (hasCache) {
    return Effect.gen(function*() {
      const cache = yield* Effect.service(Cache)
      yield* Console.log("Using cached data")
      return cache.get("user:123") || "default"
    })
  } else {
    return Effect.gen(function*() {
      yield* Console.log("No cache available, using fallback")
      return "fallback data"
    })
  }
})

const withCache = Effect.provideService(program, Cache, {
  get: () => "cached_value"
})

See

• context for reading the complete context as a value
• service for reading one service from the context

Signature

declare const contextWith: <R, A, E, R2>(f: (context: Context.Context<R>) => Effect<A, E, R2>) => Effect<A, E, R | R2>

Source

Since v2.0.0