<Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>Retrieves all active keys from the cache, automatically filtering out expired entries.
Example (Reading active keys)
import { Cache, Effect } from "effect"
// Basic key enumeration
const program = Effect.gen(function*() {
const cache = yield* Cache.make({
capacity: 10,
lookup: (key: string) => Effect.succeed(key.length)
})
// Add some entries to the cache
yield* Cache.get(cache, "hello")
yield* Cache.get(cache, "world")
yield* Cache.get(cache, "cache")
// Retrieve all active keys
const keys = yield* Cache.keys(cache)
console.log(Array.from(keys).sort()) // ["cache", "hello", "world"]
})combinators
Source effect/Cache.ts:122111 lines
export const const keys: <Key, A, E, R>(
self: Cache<Key, A, E, R>
) => Effect.Effect<Iterable<Key>>
Retrieves all active keys from the cache, automatically filtering out expired entries.
Example (Reading active keys)
import { Cache, Effect } from "effect"
// Basic key enumeration
const program = Effect.gen(function*() {
const cache = yield* Cache.make({
capacity: 10,
lookup: (key: string) => Effect.succeed(key.length)
})
// Add some entries to the cache
yield* Cache.get(cache, "hello")
yield* Cache.get(cache, "world")
yield* Cache.get(cache, "cache")
// Retrieve all active keys
const keys = yield* Cache.keys(cache)
console.log(Array.from(keys).sort()) // ["cache", "hello", "world"]
})
keys = <function (type parameter) Key in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>Key, function (type parameter) A in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>A, function (type parameter) E in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>E, function (type parameter) R in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>R>(self: Cache<Key, A, E, R>(parameter) self: {
map: MutableHashMap.MutableHashMap<Key, Entry<A, E>>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
interface Cache<in out Key, in out A, in out E = never, out R = never>A cache interface that provides a mutable key-value store with automatic TTL management,
capacity limits, and lookup functions for cache misses.
Example (Creating a basic cache)
import { Cache, Effect } from "effect"
// Basic cache with string keys and number values
const program = Effect.gen(function*() {
const cache = yield* Cache.make<string, number>({
capacity: 100,
lookup: (key: string) => Effect.succeed(key.length)
})
// Cache operations
const value1 = yield* Cache.get(cache, "hello") // 5
const value2 = yield* Cache.get(cache, "world") // 5
const value3 = yield* Cache.get(cache, "hello") // 5 (cached)
return [value1, value2, value3]
})
Example (Handling lookup failures)
import { Cache, Effect } from "effect"
// Cache with error handling
const program = Effect.gen(function*() {
const cache = yield* Cache.make<string, number, string>({
capacity: 10,
lookup: (key: string) =>
key === "error"
? Effect.fail("Lookup failed")
: Effect.succeed(key.length)
})
// Handle successful and failed lookups
const success = yield* Cache.get(cache, "test") // 4
const failure = yield* Effect.exit(Cache.get(cache, "error")) // Exit.fail
return { success, failure }
})
Example (Using complex keys with TTL)
import { Cache, Data, Duration, Effect } from "effect"
// Cache with complex key types and TTL
class UserId extends Data.Class<{ id: number }> {}
const program = Effect.gen(function*() {
const userCache = yield* Cache.make<UserId, string>({
capacity: 1000,
lookup: (userId: UserId) => Effect.succeed(`User-${userId.id}`),
timeToLive: Duration.minutes(5)
})
const userId = new UserId({ id: 123 })
const userName = yield* Cache.get(userCache, userId)
return userName // "User-123"
})
Cache<function (type parameter) Key in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>Key, function (type parameter) A in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>A, function (type parameter) E in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>E, function (type parameter) R in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>R>): import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<interface Iterable<T, TReturn = any, TNext = any>Iterable<function (type parameter) Key in <Key, A, E, R>(self: Cache<Key, A, E, R>): Effect.Effect<Iterable<Key>>Key>> =>
import corecore.const withFiber: <
A,
E = never,
R = never
>(
evaluate: (
fiber: FiberImpl<unknown, unknown>
) => Effect.Effect<A, E, R>
) => Effect.Effect<A, E, R>
fiber: effect.FiberImpl<unknown, unknown>(parameter) fiber: {
id: number;
interruptible: boolean;
currentOpCount: number;
currentLoopCount: number;
_stack: Array<Primitive>;
_observers: Array<(exit: Exit.Exit<A, E>) => void>;
_exit: Exit.Exit<A, E> | undefined;
_currentExit: Exit.Exit<A, E> | undefined;
_children: Set<FiberImpl<any, any>> | undefined;
_interruptedCause: Cause.Cause<never> | undefined;
_yielded: Exit.Exit<any, any> | (() => void) | undefined;
context: Context.Context<never>;
currentScheduler: Scheduler.Scheduler;
currentTracerContext: Tracer.Tracer["context"];
currentSpan: Tracer.AnySpan | undefined;
currentLogLevel: LogLevel.LogLevel;
minimumLogLevel: LogLevel.LogLevel;
currentStackFrame: StackFrame | undefined;
runtimeMetrics: Metric.FiberRuntimeMetricsService | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
_dispatcher: Scheduler.SchedulerDispatcher | undefined;
currentDispatcher: SchedulerDispatcher;
getRef: <X>(ref: Context.Reference<X>) => X;
addObserver: (cb: (exit: Exit.Exit<unknown, unknown>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit.Exit<unknown, unknown> | undefined;
evaluate: (effect: core.Primitive) => void;
runLoop: (effect: core.Primitive) => typeof core.Yield | Exit.Exit<unknown, unknown>;
getCont: <S extends core.contA | core.contE>(symbol: S) => (core.Primitive & Record<S, (value: any, fiber: effect.FiberImpl) => core.Primitive>) | undefined;
yieldWith: (value: Exit.Exit<any, any> | (() => void)) => core.Yield;
children: () => Set<Fiber.Fiber<any, any>>;
pipe: () => unknown;
setContext: (context: Context.Context<never>) => void;
currentSpanLocal: Span | undefined;
}
const now: numbernow = fiber: effect.FiberImpl<unknown, unknown>(parameter) fiber: {
id: number;
interruptible: boolean;
currentOpCount: number;
currentLoopCount: number;
_stack: Array<Primitive>;
_observers: Array<(exit: Exit.Exit<A, E>) => void>;
_exit: Exit.Exit<A, E> | undefined;
_currentExit: Exit.Exit<A, E> | undefined;
_children: Set<FiberImpl<any, any>> | undefined;
_interruptedCause: Cause.Cause<never> | undefined;
_yielded: Exit.Exit<any, any> | (() => void) | undefined;
context: Context.Context<never>;
currentScheduler: Scheduler.Scheduler;
currentTracerContext: Tracer.Tracer["context"];
currentSpan: Tracer.AnySpan | undefined;
currentLogLevel: LogLevel.LogLevel;
minimumLogLevel: LogLevel.LogLevel;
currentStackFrame: StackFrame | undefined;
runtimeMetrics: Metric.FiberRuntimeMetricsService | undefined;
maxOpsBeforeYield: number;
currentPreventYield: boolean;
_dispatcher: Scheduler.SchedulerDispatcher | undefined;
currentDispatcher: SchedulerDispatcher;
getRef: <X>(ref: Context.Reference<X>) => X;
addObserver: (cb: (exit: Exit.Exit<unknown, unknown>) => void) => () => void;
interruptUnsafe: (fiberId?: number | undefined, annotations?: Context.Context<never> | undefined) => void;
pollUnsafe: () => Exit.Exit<unknown, unknown> | undefined;
evaluate: (effect: core.Primitive) => void;
runLoop: (effect: core.Primitive) => typeof core.Yield | Exit.Exit<unknown, unknown>;
getCont: <S extends core.contA | core.contE>(symbol: S) => (core.Primitive & Record<S, (value: any, fiber: effect.FiberImpl) => core.Primitive>) | undefined;
yieldWith: (value: Exit.Exit<any, any> | (() => void)) => core.Yield;
children: () => Set<Fiber.Fiber<any, any>>;
pipe: () => unknown;
setContext: (context: Context.Context<never>) => void;
currentSpanLocal: Span | undefined;
}
FiberImpl<X>(ref: Context.Reference<X>): XgetRef(import effecteffect.const ClockRef: Context.Reference<Clock>const ClockRef: {
key: string;
Service: {
currentTimeMillisUnsafe: () => number;
currentTimeMillis: Effect<number>;
currentTimeNanosUnsafe: () => bigint;
currentTimeNanos: Effect<bigint>;
sleep: (duration: Duration.Duration) => Effect<void>;
};
defaultValue: () => Shape;
of: (this: void, self: Clock) => Clock;
context: (self: Clock) => Context.Context<never>;
use: (f: (service: Clock) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
useSync: (f: (service: Clock) => A) => Effect.Effect<A, never, never>;
Identifier: Identifier;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Clock.currentTimeMillisUnsafe(): numberReturns the current time in milliseconds unsafely.
When to use
Use to read millisecond time synchronously when you already have a Clock
service and can accept non-effectful access.
currentTimeMillisUnsafe()
return import effecteffect.const succeed: <A>(
value: A
) => Effect.Effect<A>
import IterableIterable.const filterMap: {
<A, B, X>(
f: (input: A, i: number) => Result<B, X>
): (self: Iterable<A>) => Iterable<B>
<A, B, X>(
self: Iterable<A>,
f: (input: A, i: number) => Result<B, X>
): Iterable<B>
}
self: Cache<Key, A, E, R>(parameter) self: {
map: MutableHashMap.MutableHashMap<Key, Entry<A, E>>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Cache<Key, A, E, R>.map: MutableHashMap.MutableHashMap<Key, Entry<A, E>>(property) Cache<Key, A, E, R>.map: {
backing: Map<K, V>;
buckets: Map<number, NonEmptyArray<K>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
key: Keykey, entry: Entry<A, E>(parameter) entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
}
entry: Entry<A, E>(parameter) entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
}
Entry<A, E>.expiresAt: number | undefinedexpiresAt === var undefinedundefined || entry: Entry<A, E>(parameter) entry: {
expiresAt: number | undefined;
deferred: Deferred.Deferred<A, E>;
}
Entry<A, E>.expiresAt: numberexpiresAt > const now: numbernow) {
return import ResultResult.const succeed: <A>(right: A) => Result<A>Creates a Result holding a Success value.
Details
- Use when you have a value and want to lift it into the
Result type
- The error type
E defaults to never
Example (Wrapping a value)
import { Result } from "effect"
const result = Result.succeed(42)
console.log(Result.isSuccess(result))
// Output: true
succeed(key: Keykey)
}
import MutableHashMapMutableHashMap.const remove: {
<K>(key: K): <V>(
self: MutableHashMap<K, V>
) => MutableHashMap<K, V>
<K, V>(
self: MutableHashMap<K, V>,
key: K
): MutableHashMap<K, V>
}
self: Cache<Key, A, E, R>(parameter) self: {
map: MutableHashMap.MutableHashMap<Key, Entry<A, E>>;
capacity: number;
lookup: (key: Key) => Effect.Effect<A, E, R>;
timeToLive: (exit: Exit.Exit<A, E>, key: Key) => Duration.Duration;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Cache<Key, A, E, R>.map: MutableHashMap.MutableHashMap<Key, Entry<A, E>>(property) Cache<Key, A, E, R>.map: {
backing: Map<K, V>;
buckets: Map<number, NonEmptyArray<K>>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
key: Keykey)
return import ResultResult.const failVoid: Result<never, void>Provides a pre-built failed Result whose failure value is undefined.
When to use
Use when you need a failed Result value that acts only as a control signal
without failure data.
Details
This is equivalent to Result.fail(undefined) with type
Result<never, void>, but reuses a shared Failure wrapper instead of
allocating one each time.
Example (Failing without a payload)
import { Result } from "effect"
const result = Result.failVoid
console.log(Result.isFailure(result))
// Output: true
failVoid
}))
})