17.7 Quosures

Quosures bundles expression with an environment
Use enquo() instead of enexpr() (with eval_tidy())

with2 <- function(df, expr) {
  a <- 1000
  eval_tidy(enquo(expr), df)
}

df <- data.frame(x = 1:3)
a <- 10
with2(df, x + a)
#> [1] 11 12 13

“Whenever you use a data mask, you must always use enquo() instead of enexpr().

This comes back in Chapter 20.

17.7.1 Which environment is bundled?

The environment where the expression is created (i.e. the parent of where enquo() is called)

Here, the global environment

with2 <- function(df, expr) {
  a <- 1000
  eq <- enquo(expr)
  message("with2() Parent/Calling environment: ")
  print(rlang::caller_env())
  message("with2() environment: ")
  print(rlang::current_env())
  message("Quosure details: ")
  print(eq)  # Print the details of the quosure
  eval_tidy(eq, df)
}

a <- 10000
df <- data.frame(x = 1:3)
with2(df, x + a)
#> with2() Parent/Calling environment:
#> <environment: R_GlobalEnv>
#> with2() environment:
#> <environment: 0x560e510933c8>
#> Quosure details:
#> <quosure>
#> expr: ^x + a
#> env:  global
#> [1] 10001 10002 10003

Here, the fun1() environment

fun1 <- function(df) {
  a <- 10
  message("fun1() Parent/Calling environment: ")
  print(rlang::caller_env())
  message("fun1() environment: ")
  print(rlang::current_env())
  with2(df, x + a)
}

a <- 10000
df <- data.frame(x = 1:3)
fun1(df)
#> fun1() Parent/Calling environment:
#> <environment: R_GlobalEnv>
#> fun1() environment:
#> <environment: 0x560e54dac8c8>
#> with2() Parent/Calling environment:
#> <environment: 0x560e54dac8c8>
#> with2() environment:
#> <environment: 0x560e54aa7820>
#> Quosure details:
#> <quosure>
#> expr: ^x + a
#> env:  0x560e54dac8c8
#> [1] 11 12 13