2

我已经在我正在处理的项目中对功能进行了局部化，这样我们就可以使用商定的分隔符，而不必一直告诉胶水它们。但是当我们在另一个函数中使用偏函数时，它停止工作：glue

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 包于 2021-07-09 创建 (v2.0.0 )

我的感觉是在它定义glue_query的环境中寻找要插入的对象，而不是在它被调用的环境中。这就是这里发生的事情吗？我可以指示它使用调用环境吗？我想在我的整个包裹中使用它！

编辑：我知道glue有一个.envir参数可以控制表达式在哪个环境中进行评估，但我不太确定使用什么来确保它在这里玩得很好！

4

2 回答 2

1

这似乎确实partial()使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。

于 2021-07-09T02:28:29.267 回答
1

一种替代方法是更改​​胶水的默认值，定义您的功能，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 包（v0.3.0）于 2021-07-09 创建

于 2021-07-09T02:31:50.837 回答