How to reuse arguments in an inner function?

Question

I have a function do_something that receives four arguments and calls an inner function get_options:

do_something <- function(name, amount, manufacturer="abc", width=4){ 
    opts <- get_options(amount, manufacturer = manufacturer, width = width)
}

get_options <- function(amount, manufacturer="abc", width = 4) { 
    opts <- validate_options(manufacturer, width)
}

Sometimes I do get_options(400), other times I want to override the arguments get_options(400, manufacturer = "def"), other times I call do_something("A", 400), or do_something("A", 400, width=10).

It seems like I'm being redundant by specifying the same default values for my arguments in both functions. Is there a better way to have them share these defaults?

Answer 1

You can use the ellipsis (...) and only give defaults to the lowest level function:

do_something <- function(name, amount, ...){ 
    opts <- get_options(amount, ...)
}

get_options <- function(amount, manufacturer="abc", width = 4) { 
    opts <- validate_options(manufacturer, width)
}

You should still be able to run all of the below:

get_options(400)
get_options(400, manufacturer = "def")
do_something("A", 400)
do_something("A", 400, width=10)

and with the same results.