once

Documentation

Overview

once contains helpers for constructing type-safe, concurrency-safe values that are only ever initialized once, and can potentially return an error.

Index

• type Map
  • func NewMap[K comparable, V any]() Map[K, V]
• type Var
  • func NewVar[T any]() Var[T]

Types

type Map

type Map[K comparable, V any] interface {
	// Set initializes the key K at most one time, and returns the result.
	Set(K, func() (*V, error)) (*V, error)
	// Get returns the initialization result associated with the key K.
	// If K has not yet been initialized, the result will be (<nil>, <nil>).
	Get(K) (*V, error)
}

Map is a type-safe and concurrency-safe implementation of a map where each entry is initialized a single time.

func NewMap

func NewMap[K comparable, V any]() Map[K, V]

NewMap returns a Map, a type-safe and concurrency-safe implementation of a map where each entry is initialized a single time.

type Var

type Var[T any] interface {
	// Set initializes the var at most one time, and returns the result.
	// If K has not yet been initialized, the result will be (<nil>, <nil>).
	Set(func() (*T, error)) (*T, error)
	// Get returns the initialized result. If the var has not yet been
	// initialized, the result will be (<nil>, <nil>)
	Get() (*T, error)
}

Var is a type-safe and concurrency-safe wrapper for a value that is initialized a single time.

func NewVar

func NewVar[T any]() Var[T]

NewVar returns a Var, a type-safe and concurrency-safe wrapper for a value that is initialized a single time.