(self: MutableRef<number>): numberDecrements a numeric MutableRef by 1 and returns the previous value.
When to use
Use to read the current numeric MutableRef value before decrementing it.
Example (Reading before decrementing)
import { MutableRef } from "effect"
const counter = MutableRef.make(5)
// Get current value and then decrement
const previousValue = MutableRef.getAndDecrement(counter)
console.log(previousValue) // 5
console.log(MutableRef.get(counter)) // 4
// Useful for processing where you need the original value
const itemsLeft = MutableRef.make(10)
while (MutableRef.get(itemsLeft) > 0) {
const currentItem = MutableRef.getAndDecrement(itemsLeft)
console.log(`Processing item ${currentItem}`)
}
// Post-decrement semantics (like i-- in other languages)
const index = MutableRef.make(3)
const currentIndex = MutableRef.getAndDecrement(index)
console.log(`Current: ${currentIndex}, Next: ${MutableRef.get(index)}`) // "Current: 3, Next: 2"numeric
Source effect/MutableRef.ts:3181 lines
export const const getAndDecrement: (
self: MutableRef<number>
) => number
Decrements a numeric MutableRef by 1 and returns the previous value.
When to use
Use to read the current numeric MutableRef value before decrementing it.
Example (Reading before decrementing)
import { MutableRef } from "effect"
const counter = MutableRef.make(5)
// Get current value and then decrement
const previousValue = MutableRef.getAndDecrement(counter)
console.log(previousValue) // 5
console.log(MutableRef.get(counter)) // 4
// Useful for processing where you need the original value
const itemsLeft = MutableRef.make(10)
while (MutableRef.get(itemsLeft) > 0) {
const currentItem = MutableRef.getAndDecrement(itemsLeft)
console.log(`Processing item ${currentItem}`)
}
// Post-decrement semantics (like i-- in other languages)
const index = MutableRef.make(3)
const currentIndex = MutableRef.getAndDecrement(index)
console.log(`Current: ${currentIndex}, Next: ${MutableRef.get(index)}`) // "Current: 3, Next: 2"
getAndDecrement = (self: MutableRef<number>(parameter) self: {
current: T;
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;
}
interface MutableRef<out T>A synchronous mutable reference that stores a current value.
When to use
Use to keep local mutable state in a stable, pipeable reference.
Details
Read or write the value directly through .current, or use the MutableRef
helpers for pipeable updates such as get, set, update, and
compareAndSet. All operations mutate the same reference in place.
Example (Creating and updating refs)
import { MutableRef } from "effect"
// Create a mutable reference
const ref: MutableRef.MutableRef<number> = MutableRef.make(42)
// Read the current value
console.log(ref.current) // 42
console.log(MutableRef.get(ref)) // 42
// Update the value
ref.current = 100
console.log(MutableRef.get(ref)) // 100
// Use with complex types
interface Config {
timeout: number
retries: number
}
const config: MutableRef.MutableRef<Config> = MutableRef.make({
timeout: 5000,
retries: 3
})
// Update through the interface
config.current = { timeout: 10000, retries: 5 }
console.log(config.current.timeout) // 10000
MutableRef<number>): number => const getAndUpdate: {
<T>(f: (value: T) => T): (
self: MutableRef<T>
) => T
<T>(self: MutableRef<T>, f: (value: T) => T): T
}
self: MutableRef<number>(parameter) self: {
current: T;
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;
}
n: numbern) => n: numbern - 1)