Get or set the environment of an objectSource:
These functions dispatch internally with methods for functions,
formulas and frames. If called with a missing argument, the
environment of the current evaluation frame is returned. If you
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)
The default environment in case
envdoes not wrap an environment. If
NULLand no environment could be extracted, an error is issued.
An environment to replace
set_env() returns a modified copy and does not have side
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
quo_set_env() for versions of
set_env() that only work on quosures.
# Environment of closure functions: fn <- function() "foo" get_env(fn) #> <environment: 0x55812eb136b0> # Or of quosures or formulas: get_env(~foo) #> <environment: 0x55812eb136b0> get_env(quo(foo)) #> <environment: 0x55812eb136b0> # 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) #>  TRUE # 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) #>  TRUE identical(get_env(fn), current_env()) #>  FALSE # 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) #> function() NULL #> <environment: 0x55812e2e8b28> identical(get_env(fn), other_env) #>  FALSE # 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) #>  TRUE