# poke_vars

##### Replace or get current variables

Variables are made available to select helpers by registering them in a special placeholder.

`scoped_vars()`

changes the current variables and sets up a function exit hook that automatically restores the previous variables once the current function returns.`with_vars()`

takes an expression to be evaluated in a variable context.`poke_vars()`

changes the contents of the placeholder with a new set of variables. It returns the previous variables invisibly and it is your responsibility to restore them after you are done. This is for expert use only.`peek_vars()`

returns the variables currently registered.

##### Usage

`poke_vars(vars)`peek_vars()

scoped_vars(vars, frame = caller_env())

with_vars(vars, expr)

##### Arguments

- vars
A character vector of variable names.

- frame
The frame environment where the exit hook for restoring the old variables should be registered.

- expr
An expression to be evaluated within the variable context.

##### Value

For `poke_vars()`

and `scoped_vars()`

, the old variables
invisibly. For `peek_vars()`

, the variables currently
registered.

##### Examples

```
# NOT RUN {
poke_vars(letters)
peek_vars()
# Now that the variables are registered, the helpers can figure out
# the positions of elements within the variable vector:
one_of(c("d", "z"))
# In a function be sure to restore the previous variables. An exit
# hook is the best way to do it:
fn <- function(vars) {
old <- poke_vars(vars)
on.exit(poke_vars(old))
one_of("d")
}
fn(letters)
fn(letters[3:5])
# The previous variables are still registered after fn() was
# called:
peek_vars()
# It is recommended to use the scoped variant as it restores the
# state automatically when the function returns:
fn <- function(vars) {
scoped_vars(vars)
starts_with("r")
}
fn(c("red", "blue", "rose"))
# The with_vars() helper makes it easy to pass an expression that
# should be evaluated in a variable context. Thanks to lazy
# evaluation, you can just pass the expression argument from your
# wrapper to with_vars():
fn <- function(expr) {
vars <- c("red", "blue", "rose")
with_vars(vars, expr)
}
fn(starts_with("r"))
# }
```

*Documentation reproduced from package tidyselect, version 0.1.1, License: GPL-3*