在不同环境中调用时，局部粘合功能不起作用

Question

我 partialised the glue function 在我正在进行的一个项目中，这样我们就可以使用商定的分隔符，而不必一直告诉 glue。但是当我们在另一个函数中使用偏函数时，它停止工作：

library(purrr)
library(glue)

glue_query <- partial(glue, .open = "<<", .close = ">>")

# case 1: use partialised function in same scope
x <- 15
glue_query("There are <<x>> apples here!")
#> There are 15 apples here!

# case 2: use partialised function in different scope
myfunc_partialised <- function(y) {
  glue_query("The thing I called y is actually <<y>>")
}
myfunc_partialised(15)
#> Error in eval(parse(text = text, keep.source = FALSE), envir): object 'y' not found

# case 3: use function directly
myfunc_regular <- function(z) {
  glue("The thing I called z is actually <<z>>", .open = "<<", .close = ">>")
}
myfunc_regular(15)
#> The thing I called z is actually 15

^{由 reprex package (v2.0.0)}

于 2021-07-09 创建

我觉得 glue_query 正在寻找要在 定义的 环境中插入的对象，而不是在 的环境中called in. 这就是这里发生的事情吗？我可以指示它使用调用环境吗？我想在我的包裹中使用它！

编辑： 我知道 glue 有一个 .envir 参数控制表达式在哪个环境中求值，但我不太确定使用什么来确保它在这里播放得很好！

Answer 1

看来 partial() 确实让获得正确的环境变得更加困难。相反，您可以编写自己的包装器

glue_query <- function(..., .open = "<<", .close = ">>", .envir=parent.frame()) {
  glue(..., .open=.open, .close=.close, .envir=.envir)
}

这将适用于您提供的两个测试用例。

Answer 2

一种替代方法是更改胶水的默认值，定义您的函数，然后重置默认值：

library(glue)
library(default)

default(glue) <- list(.open = "<<", .close = ">>")
glue2 <- glue
reset_default(glue)
#> function (..., .sep = "", .envir = parent.frame(), .open = "{", 
#>     .close = "}", .na = "NA", .transformer = identity_transformer, 
#>     .trim = TRUE) 
#> {
#>     glue_data(.x = NULL, ..., .sep = .sep, .envir = .envir, .open = .open, 
#>         .close = .close, .na = .na, .transformer = .transformer, 
#>         .trim = .trim)
#> }
#> <bytecode: 0x0000000014c59d80>
#> <environment: namespace:glue>

# case 1: use partialised function in same scope
x <- 15
glue_query("There are <<x>> apples here!")
#> Error in glue_query("There are <<x>> apples here!"): could not find function "glue_query"
#> There are 15 apples here!

# case 2: use partialised function in different scope
myfunc_partialised <- function(y) {
  glue2("The thing I called y is actually <<y>>")
}
myfunc_partialised(15)
#> The thing I called y is actually 15

# case 3: use function directly
myfunc_regular <- function(z) {
  glue("The thing I called z is actually <<z>>", .open = "<<", .close = ">>")
}
myfunc_regular(15)
#> The thing I called z is actually 15

^{由 reprex package (v0.3.0)}

于 2021-07-09 创建

在不同环境中调用时，局部粘合功能不起作用

Partialised glue function does not work when called in different environment

r

purrr

r-environment

r-glue