问题描述
我在我正在处理的项目中使用了 partialised glue
function,这样我们就可以使用商定的分隔符,而不必一直告诉胶水。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>>",.close = ">>")
}
myfunc_regular(15)
#> The thing I called z is actually 15
由 reprex package (v2.0.0) 于 2021 年 7 月 9 日创建
我感觉 glue_query
正在寻找要在它定义的环境中插入的对象,而不是在它调用的环境中。这就是这里发生的事情吗?我可以指导它使用调用环境吗?我想在我的整个包裹中使用它!
编辑:我知道 glue
有一个 .envir
参数来控制表达式在哪个环境中计算,但我不太确定使用什么来确保在这里玩得很好!
解决方法
似乎 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。
,另一种选择是更改胶水的默认值,定义您的函数,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>>",.close = ">>")
}
myfunc_regular(15)
#> The thing I called z is actually 15
由 reprex package (v0.3.0) 于 2021 年 7 月 9 日创建