define REDCap constants

[wibeasley]

centrally define constants. Right now, I'm frequently re-defining these at the top of a lot of R files to avoid magic constants sprinkled throughout the code. There could be more than this, but currently I'd use

• form_incomplete = 1 0
• form_unverified = 2 1
• form_complete = 3 2

These values might be contained in a single list called constant, so the caller's code might look like

ds <- ds %>%
  dplyr::mutate(
    bookkeeping_complete   = REDCapR::constant$form_unverified
  )

Alternatively, there could be a function called constant(), that accepts the name. The function would check to see if the constant is even defined, instead of returning NULL. The caller's code might look like

ds <- ds %>%
  dplyr::mutate(
    bookkeeping_complete   = REDCapR::constant("form_unverified")
  )

Any opinions? If anyone has experience with this, or might have a better way, please tell me.

[nutterb]

I would define each constant separately. As long as they aren't exported, it won't create any issues for the user.

For your own sanity, I'd recommend naming them with an underscore in front, just to give a visual cue that it is an internal constant. So _form_incomplete = 1, for example.

[wibeasley]

@nutterb, I was thinking I would export them, so all my external code wouldn't have to define them. Do you think that's a bad idea?

[nutterb]

Not a bad idea at all. It just escaped me that you intended this for direct user access (I'm sleep deprived).

I like how you have this set up currently, with constant_list being unexported, but accessible through a function.

I might add checkmate::assert_logical(simplify, len = 1) to your checks.