<K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>Returns an immutable snapshot of the current TxHashMap state.
Example (Taking immutable snapshots)
import { Effect, HashMap, TxHashMap } from "effect"
const program = Effect.gen(function*() {
const liveData = yield* TxHashMap.make(
["temperature", 22.5],
["humidity", 45.2],
["pressure", 1013.25]
)
// Take snapshot for reporting
const snapshot = yield* TxHashMap.snapshot(liveData)
// Continue modifying live data
yield* TxHashMap.set(liveData, "temperature", 23.1)
yield* TxHashMap.set(liveData, "wind_speed", 5.3)
// Snapshot remains unchanged
console.log(HashMap.size(snapshot)) // 3
console.log(HashMap.get(snapshot, "temperature")) // Option.some(22.5)
// Can use regular HashMap operations on snapshot
const tempReading = HashMap.get(snapshot, "temperature")
const humidityReading = HashMap.get(snapshot, "humidity")
})combinators
Source effect/TxHashMap.ts:9803 lines
export const const snapshot: <K, V>(
self: TxHashMap<K, V>
) => Effect.Effect<HashMap.HashMap<K, V>>
Returns an immutable snapshot of the current TxHashMap state.
Example (Taking immutable snapshots)
import { Effect, HashMap, TxHashMap } from "effect"
const program = Effect.gen(function*() {
const liveData = yield* TxHashMap.make(
["temperature", 22.5],
["humidity", 45.2],
["pressure", 1013.25]
)
// Take snapshot for reporting
const snapshot = yield* TxHashMap.snapshot(liveData)
// Continue modifying live data
yield* TxHashMap.set(liveData, "temperature", 23.1)
yield* TxHashMap.set(liveData, "wind_speed", 5.3)
// Snapshot remains unchanged
console.log(HashMap.size(snapshot)) // 3
console.log(HashMap.get(snapshot, "temperature")) // Option.some(22.5)
// Can use regular HashMap operations on snapshot
const tempReading = HashMap.get(snapshot, "temperature")
const humidityReading = HashMap.get(snapshot, "humidity")
})
snapshot = <function (type parameter) K in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>K, function (type parameter) V in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>V>(
self: TxHashMap<K, V>(parameter) self: {
ref: TxRef.TxRef<HashMap.HashMap<K, V>>;
toString: () => string;
toJSON: () => unknown;
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 TxHashMap<in out K, in out V>A TxHashMap is a transactional hash map data structure that provides atomic operations
on key-value pairs within Effect transactions. It uses an immutable HashMap internally
with TxRef for transactional semantics, ensuring all operations are performed atomically.
Example (Using transactional hash maps)
import { Effect, TxHashMap } from "effect"
const program = Effect.gen(function*() {
// Create a transactional hash map
const txMap = yield* TxHashMap.make(["user1", "Alice"], ["user2", "Bob"])
// Single operations are automatically transactional
yield* TxHashMap.set(txMap, "user3", "Charlie")
const user = yield* TxHashMap.get(txMap, "user1")
console.log(user) // Option.some("Alice")
// Multi-step atomic operations
yield* Effect.tx(
Effect.gen(function*() {
const currentUser = yield* TxHashMap.get(txMap, "user1")
if (currentUser._tag === "Some") {
yield* TxHashMap.set(txMap, "user1", currentUser.value + "_updated")
yield* TxHashMap.remove(txMap, "user2")
}
})
)
const size = yield* TxHashMap.size(txMap)
console.log(size) // 2
})
The TxHashMap namespace contains type-level utilities and helper types
for working with TxHashMap instances.
Example (Reusing extracted TxHashMap types)
import { Effect, TxHashMap } from "effect"
const program = Effect.gen(function*() {
// Create a transactional inventory map
const inventory = yield* TxHashMap.make(
["laptop", { stock: 5, price: 999 }],
["mouse", { stock: 20, price: 29 }]
)
// Extract types for reuse
type ProductId = TxHashMap.TxHashMap.Key<typeof inventory> // string
type Product = TxHashMap.TxHashMap.Value<typeof inventory> // { stock: number, price: number }
type InventoryEntry = TxHashMap.TxHashMap.Entry<typeof inventory> // [string, Product]
// Use extracted types in functions
const updateStock = (id: ProductId, newStock: number) =>
TxHashMap.modify(
inventory,
id,
(product) => ({ ...product, stock: newStock })
)
yield* updateStock("laptop", 3)
})
TxHashMap<function (type parameter) K in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>K, function (type parameter) V in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>V>
): import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<import HashMapHashMap.type HashMap.HashMap = /*unresolved*/ anyHashMap<function (type parameter) K in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>K, function (type parameter) V in <K, V>(self: TxHashMap<K, V>): Effect.Effect<HashMap.HashMap<K, V>>V>> => import TxRefTxRef.const get: <A>(
self: TxRef<A>
) => Effect.Effect<A>
Reads the current value of the TxRef.
When to use
Use to read the current value of a TxRef.
Example (Reading transactional references)
import { Effect, TxRef } from "effect"
const program = Effect.gen(function*() {
const counter = yield* TxRef.make(42)
// Read the value within a transaction
const value = yield* Effect.tx(
TxRef.get(counter)
)
console.log(value) // 42
})
get(self: TxHashMap<K, V>(parameter) self: {
ref: TxRef.TxRef<HashMap.HashMap<K, V>>;
toString: () => string;
toJSON: () => unknown;
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; <…;
}
TxHashMap<in out K, in out V>.ref: TxRef.TxRef<HashMap.HashMap<K, V>>(property) TxHashMap<in out K, in out V>.ref: {
version: number;
pending: Map<unknown, () => void>;
value: A;
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; <…;
}