new_quosure {rlang}

Create a quosure from components

Description

• new_quosure() wraps any R object (including expressions, formulas, or other quosures) into a quosure.

• as_quosure() is similar but it does not rewrap formulas and quosures.

Usage

new_quosure(expr, env = caller_env())

as_quosure(x, env = NULL)

is_quosure(x)

Arguments

expr

An expression to wrap in a quosure.

env

The environment in which the expression should be evaluated. Only used for symbols and calls. This should normally be the environment in which the expression was created.

x

An object to test.

See Also

• enquo() and quo() for creating a quosure by argument defusal.

• What are quosures and when are they needed?

Examples

# `new_quosure()` creates a quosure from its components. These are
# equivalent:
new_quosure(quote(foo), current_env())

quo(foo)

# `new_quosure()` always rewraps its input into a new quosure, even
# if the input is itself a quosure:
new_quosure(quo(foo))

# This is unlike `as_quosure()` which preserves its input if it's
# already a quosure:
as_quosure(quo(foo))


# `as_quosure()` uses the supplied environment with naked expressions:
env <- env(var = "thing")
as_quosure(quote(var), env)

# If the expression already carries an environment, this
# environment is preserved. This is the case for formulas and
# quosures:
as_quosure(~foo, env)

as_quosure(~foo)

# An environment must be supplied when the input is a naked
# expression:
try(
  as_quosure(quote(var))
)