env_cache: Cache a value in an environment

In hadley/rlang: Functions for Base Types and Core R and 'Tidyverse' Features

Cache a value in an environment

Description

env_cache() is a wrapper around env_get() and env_poke() designed to retrieve a cached value from env.

• If the nm binding exists, it returns its value.

• Otherwise, it stores the default value in env and returns that.

Usage

env_cache(env, nm, default)

Arguments

env	An environment.
nm	Name of binding, a string.
default	The default value to store in env if nm does not exist yet.

Value

Either the value of nm or default if it did not exist yet.

Examples

e <- env(a = "foo")

# Returns existing binding
env_cache(e, "a", "default")

# Creates a `b` binding and returns its default value
env_cache(e, "b", "default")

# Now `b` is defined
e$b

hadley/rlang documentation built on Dec. 17, 2024, 3:26 a.m.