I'm using tidyselection in some function, and I have to concatenate the first argument with the ellipsis as it could be a specific class that would need a specific treatment.
The normal behavior is this:
foo = function(x, ...){
xloc = eval_select(expr(c(x, ...)), data = iris)
return(xloc)
}
foo(everything())
I want to have everything() as the default value when x is NULL (I cannot put it directly in the header for some reason).
Unfortunately, this syntax is not allowed:
bar = function(x, ...){
if(is_null(x))
x=everything() #throws an error
xloc = eval_select(expr(c(x, ...)), data = iris)
return(xloc)
}
bar(NULL)
# Error: `everything()` must be used within a *selecting* function.
# i See <https://tidyselect.r-lib.org/reference/faq-selection-context.html>.
I tried to wrap everything() with all "mystic" functions I know: parse, deparse, call, substitute, quo, sym, enquo, ensym, ... Nothing worked (you can see here that I don't master these very well).
With what expression can I replace my x=everything() line in my second code chunk for this function to work?
Versions:
First you need to pass x via {{, otherwise the argument can't be inspected by tidyselect, and some features won't work properly. Then you can give it a default of everything():
foo <- function(x = everything(), ...) {
eval_select(expr(c({{ x }}, ...)), data = iris)
}
foo(everything())
#> Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1 2 3 4 5
foo()
#> Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#> 1 2 3 4 5
If you can' use default arguments for some reason, defuse everything() manually then force it with !!:
foo <- function(x = NULL, ...) {
x <- enquo(x)
if (quo_is_null(x)) {
x <- expr(everything())
}
eval_select(expr(c(!!x, ...)), data = iris)
}