S7 Workaround

[andrewallenbruce]

Thanks for the workaround! I was able to apply it to my real use case.

Just for reference to anyone else reading this, here's what you'd do if you still want to rely on referencing an external object (the penguins data frame) to get the property names:

library(S7)
library(rlang)
library(purrr)
library(palmerpenguins)

my_penguin <- as.list(penguins[1,])

penguin <- new_class(
  "penguin",
  properties = list(
    species = class_factor,
    island = class_factor,
    bill_length_mm = class_double,
    bill_depth_mm = class_double,
    flipper_length_mm = class_integer,
    body_mass_g = class_integer,
    sex = class_factor,
    year = class_integer
  ),
  constructor = function(x) {
    props <- set_names(colnames(penguins)) # Get prop names from `penguins` tbl
    prop_vals <- map(props, function(prop_name) pluck(x, prop_name))

    # hack to enable using `new_object()` with NSE.
    constructor <- function() {}
    body(constructor) <- inject(quote(new_object(S7_object(), !!!prop_vals)))
    attributes(constructor) <- attributes(sys.function())
    constructor()
  }
)

penguin(my_penguin)
#> <penguin>
#>  @ species          : Factor w/ 3 levels "Adelie","Chinstrap",..: 1
#>  @ island           : Factor w/ 3 levels "Biscoe","Dream",..: 3
#>  @ bill_length_mm   : num 39.1
#>  @ bill_depth_mm    : num 18.7
#>  @ flipper_length_mm: int 181
#>  @ body_mass_g      : int 3750
#>  @ sex              : Factor w/ 2 levels "female","male": 2
#>  @ year             : int 2007

^{Created on 2024-11-19 with reprex v2.1.1}

Originally posted by @mccarthy-m-g in RConsortium/S7#497 (comment)