Get or set the environment of an object
These functions dispatch internally with methods for functions,
formulas and frames. If called with a missing argument, the
environment of the current evaluation frame (see ctxt_stack()) is
returned. If you call get_env() with an environment, it acts as
the identity function and the environment is simply returned (this
helps simplifying code when writing generic functions for
environments).
get_env(env, default = NULL) set_env(env, new_env = caller_env()) env_poke_parent(env, new_env)
env |
An environment. |
default |
The default environment in case |
new_env |
An environment to replace |
While set_env() returns a modified copy and does not have side
effects, env_poke_parent() operates changes the environment by
side effect. This is because environments are
uncopyable. Be careful not to change environments
that you don't own, e.g. a parent environment of a function from a
package.
Using get_env() without supplying env is deprecated as
of rlang 0.3.0. Please use current_env() to retrieve the
current environment.
Passing environment wrappers like formulas or functions instead of bare environments is deprecated as of rlang 0.3.0. This internal genericity was causing confusion (see issue #427). You should now extract the environment separately before calling these functions.
quo_get_env() and quo_set_env() for versions of
get_env() and set_env() that only work on quosures.
# Environment of closure functions:
fn <- function() "foo"
get_env(fn)
# Or of quosures or formulas:
get_env(~foo)
get_env(quo(foo))
# Provide a default in case the object doesn't bundle an environment.
# Let's create an unevaluated formula:
f <- quote(~foo)
# The following line would fail if run because unevaluated formulas
# don't bundle an environment (they didn't have the chance to
# record one yet):
# get_env(f)
# It is often useful to provide a default when you're writing
# functions accepting formulas as input:
default <- env()
identical(get_env(f, default), default)
# set_env() can be used to set the enclosure of functions and
# formulas. Let's create a function with a particular environment:
env <- child_env("base")
fn <- set_env(function() NULL, env)
# That function now has `env` as enclosure:
identical(get_env(fn), env)
identical(get_env(fn), current_env())
# set_env() does not work by side effect. Setting a new environment
# for fn has no effect on the original function:
other_env <- child_env(NULL)
set_env(fn, other_env)
identical(get_env(fn), other_env)
# Since set_env() returns a new function with a different
# environment, you'll need to reassign the result:
fn <- set_env(fn, other_env)
identical(get_env(fn), other_env)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.