Coerce to a function

to_fn() coerces x to a function. to_function() is a synonym of to_fn().

Usage

to_fn(
  x,
  ...,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

to_function(
  x,
  ...,
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

# S3 method for class '`NULL`'
to_fn(x, ..., allow_null = TRUE, x_arg = caller_arg(x), call = caller_env())

# S3 method for class 'character'
to_fn(
  x,
  ...,
  allow_null = TRUE,
  definition_env = rlang::global_env(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

# Default S3 method
to_fn(
  x,
  ...,
  definition_env = rlang::global_env(),
  x_arg = caller_arg(x),
  call = caller_env(),
  x_class = object_type(x)
)

Arguments

x

The argument to stabilize.

...

Arguments passed to methods.

x_arg

(length-1 character) The name of the argument being stabilized to use in error messages. The automatic value will work in most cases, or pass it through from higher-level functions to make error messages clearer in unexported functions.

call

(environment) The execution environment to mention as the source of error messages.

x_class

(length-1 character) The class name of the argument being stabilized to use in error messages. Use this if you remove a special class from the object before checking its coercion, but want the error message to match the original class.

allow_null

(length-1 logical) Is NULL an acceptable value?

definition_env

(environment) The environment in which to look up function name. Defaults to rlang::global_env(). This argument is ignored when the input is a namespaced string of the form "pkg::fn", in which case the package namespace is used instead.

Value

A function.

Details

Unlike rlang::as_function(), to_fn() supports namespaced function names such as "pkg::fn" in the character method. When the input is a length-0 character vector, to_fn() returns NULL (subject to allow_null). An input of length > 1 is always an error.

See also

Other function functions: are_fn_ish(), to()

Examples

to_fn("mean")
#> function (x, ...) 
#> UseMethod("mean")
#> <bytecode: 0x563b33588500>
#> <environment: namespace:base>
to_fn(~ . + 1)
#> <lambda>
#> function (..., .x = ..1, .y = ..2, . = ..1) 
#> . + 1
#> <environment: 0x563b3a5febf0>
#> attr(,"class")
#> [1] "rlang_lambda_function" "function"             
to_fn(mean)
#> function (x, ...) 
#> UseMethod("mean")
#> <bytecode: 0x563b33588500>
#> <environment: namespace:base>
to_fn("stats::median")
#> function (x, na.rm = FALSE, ...) 
#> UseMethod("median")
#> <bytecode: 0x563b32f43a48>
#> <environment: namespace:stats>
to_fn(NULL)
#> NULL