meta programming - want to refer to users name for object in print method

[njtierney]

Hi there!

I'd like to be able to refer to the name of the object that the user has created, in a print method.

Here's a small example, I've got two functions - one of them when I call it on the base data set airquality, which works when I call the function, my_info directly, but when I call my_info inside of another function I lose reference to that name.

I get the sense that I might need to try and do deparse(substitute()) or some variant but specifying the original environment? Or perhaps I need to pass in the environment along with x - I'm just not sure!

If anyone has any thoughts/ideas, I'd love to hear them

Cheers!

my_info <- function(x){
  obj_name <- deparse(substitute(x))
  cli::cli_alert_info("Access column names with {obj_name}$<var>")
  cli::cli_alert_info("e.g., {obj_name}${names(x)[1]}")
}

my_print <- function(x){
  cli::cli_h1("My Object")
  cli::cli_text("My dims are {dim(x)}")
  my_info(x)
}

# this prints "airquality"
my_info(airquality)
#> ℹ Access column names with airquality$<var>
#> ℹ e.g., airquality$Ozone

# this doesn't print "airquality"
my_print(airquality)
#> 
#> ── My Object ───────────────────────────────────────────────────────────────────
#> My dims are 153 and 6
#> ℹ Access column names with x$<var>
#> ℹ e.g., x$Ozone

^{Created on 2022-12-22 with reprex v2.0.2}

Session info

sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value
#>  version  R version 4.2.1 (2022-06-23)
#>  os       macOS Monterey 12.3.1
#>  system   aarch64, darwin20
#>  ui       X11
#>  language (EN)
#>  collate  en_US.UTF-8
#>  ctype    en_US.UTF-8
#>  tz       Australia/Brisbane
#>  date     2022-12-22
#>  pandoc   2.19.2 @ /Applications/RStudio.app/Contents/Resources/app/quarto/bin/tools/ (via rmarkdown)
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package     * version date (UTC) lib source
#>  cli           3.4.1   2022-09-23 [1] CRAN (R 4.2.0)
#>  digest        0.6.30  2022-10-18 [1] CRAN (R 4.2.0)
#>  evaluate      0.18    2022-11-07 [1] CRAN (R 4.2.0)
#>  fastmap       1.1.0   2021-01-25 [1] CRAN (R 4.2.0)
#>  fs            1.5.2   2021-12-08 [1] CRAN (R 4.2.0)
#>  glue          1.6.2   2022-02-24 [1] CRAN (R 4.2.0)
#>  highr         0.9     2021-04-16 [1] CRAN (R 4.2.0)
#>  htmltools     0.5.3   2022-07-18 [1] CRAN (R 4.2.0)
#>  knitr         1.41    2022-11-18 [1] CRAN (R 4.2.0)
#>  lifecycle     1.0.3   2022-10-07 [1] CRAN (R 4.2.0)
#>  magrittr      2.0.3   2022-03-30 [1] CRAN (R 4.2.0)
#>  purrr         0.3.5   2022-10-06 [1] CRAN (R 4.2.0)
#>  R.cache       0.16.0  2022-07-21 [1] CRAN (R 4.2.0)
#>  R.methodsS3   1.8.2   2022-06-13 [1] CRAN (R 4.2.0)
#>  R.oo          1.25.0  2022-06-12 [1] CRAN (R 4.2.0)
#>  R.utils       2.12.2  2022-11-11 [1] CRAN (R 4.2.0)
#>  reprex        2.0.2   2022-08-17 [1] CRAN (R 4.2.0)
#>  rlang         1.0.6   2022-09-24 [1] CRAN (R 4.2.0)
#>  rmarkdown     2.18    2022-11-09 [1] CRAN (R 4.2.0)
#>  rstudioapi    0.14    2022-08-22 [1] CRAN (R 4.2.0)
#>  sessioninfo   1.2.2   2021-12-06 [1] CRAN (R 4.2.0)
#>  stringi       1.7.8   2022-07-11 [1] CRAN (R 4.2.0)
#>  stringr       1.5.0   2022-12-02 [1] CRAN (R 4.2.0)
#>  styler        1.8.1   2022-11-07 [1] CRAN (R 4.2.0)
#>  vctrs         0.5.1   2022-11-16 [1] CRAN (R 4.2.0)
#>  withr         2.5.0   2022-03-03 [1] CRAN (R 4.2.0)
#>  xfun          0.35    2022-11-16 [1] CRAN (R 4.2.0)
#>  yaml          2.3.6   2022-10-18 [1] CRAN (R 4.2.0)
#> 
#>  [1] /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/library
#> 
#> ──────────────────────────────────────────────────────────────────────────────

[nirgrahamuk]

seems to work

my_info <- function(x){
  obj_name <- deparse(substitute(x))
  cli::cli_alert_info("Access column names with {obj_name}$<var>")
  cli::cli_alert_info("e.g., {obj_name}${names(x)[1]}")
}

my_print <- function(x){
  obj_name <- deparse(substitute(x))
  cli::cli_h1("My Object")
  cli::cli_text("My dims are {dim(x)}")
  eval(parse(text=cli:::glue("my_info({obj_name})")))
}

my_info(airquality)
my_print(airquality)

[assignUser]

You can pass an environment to substitute from which it will pull. For the function to work as intended when it is not called in a nested function we set it to the current env. In nested functions you just pass the current (parent for the function) env.

library(cli)
my_info <- function(x, env = environment()){
  obj_name <- deparse(substitute(x, env))
  cli::cli_alert_info("Access column names with {obj_name}$<var>")
  cli::cli_alert_info("e.g., {obj_name}${names(x)[1]}")
}

my_print <- function(x){
  cli::cli_h1("My Object")
  cli::cli_text("My dims are {dim(x)}")
  my_info(x, environment())
}

my_info(airquality)
#> ℹ Access column names with airquality$<var>
#> ℹ e.g., airquality$Ozone

my_print(airquality)
#> 
#> ── My Object ───────────────────────────────────────────────────────────────────
#> My dims are 153 and 6
#> ℹ Access column names with airquality$<var>
#> ℹ e.g., airquality$Ozone

[nirgrahamuk]

This is much better than my hack

[njtierney]

This is just fantastic! Thank you very much, @assignUser !!!