我有一个函数 foo()
,我希望能够以两种不同的“模式”调用它:一次或在 while 循环内调用。
我认为使用某种通用的包装器(runtime_gateway()
)并通过...
将参数传递给foo()
是有意义的在这里,我可以利用相同的“运行时网关逻辑”来实现具有不同参数集的任意函数。
如果在 while 循环内运行 foo()
,我想更新其一些参数,同时保留默认值或传递的参数其他参数的值。
我该怎么做?
我知道 rlang::dot_list(...)
和 friend ,并快速浏览了 https://github.com/r-lib/ellipsis 。似乎其中任何一个都只能从省略号内容中提取值或检查省略号内容,但我不知道如何“在传输过程中更新它”。
Reprex
foo <- function(
id = "id_a",
at = Sys.time()
) {
message(stringr::str_glue("{id}: {at}"))
Sys.sleep(1)
}
runtime_gateway <- function(
fun = foo,
run_mode = c("once", "while"),
... # Args to be passed to `fun`
) {
run_mode <- match.arg(run_mode)
if (run_mode == "once") {
fun(...)
} else if (run_mode == "while") {
counter <- 0
while(counter < 3) {
# Goal: keep ellipsis value for `id` but *update* value for `at`
dots <- rlang::dots_list(...)
at <- if ("at" %in% names(dots)) {
message("`at` was passed via ellipsis:")
message(dots$at)
dots$at
} else {
Sys.time()
}
fun(at = at + 60, ...)
counter <- counter + 1
}
}
}
runtime_gateway()
#> id_a: 2020-02-21 14:09:16.779
runtime_gateway(at = lubridate::ymd_hms("2020-02-21 10:30:00"))
#> id_a: 2020-02-21 10:30:00
runtime_gateway(run_mode = "while")
#> id_a: 2020-02-21 14:10:18.897
#> id_a: 2020-02-21 14:10:19.900
#> id_a: 2020-02-21 14:10:20.902
runtime_gateway(run_mode = "while", id = "id_b")
#> id_b: 2020-02-21 14:10:21.905
#> id_b: 2020-02-21 14:10:22.906
#> id_b: 2020-02-21 14:10:23.908
runtime_gateway(run_mode = "while", at = lubridate::ymd_hms("2020-02-21 10:30:00"))
#> `at` was passed via ellipsis:
#> 2020-02-21 10:30:00
#> Error in fun(at = at + 60, ...): formal argument "at" matched by multiple actual arguments
由reprex package于2020年2月21日创建(v0.3.0)
最佳答案
您可以通过添加 dots
参数(如果不存在)来确保它包含 at
参数,然后使用 分派(dispatch)
而不是fun
点...
与do.call
runtime_gateway <- function(
fun = foo,
run_mode = c("once", "while"),
... # Args to be passed to `fun`
) {
run_mode <- match.arg(run_mode)
if (run_mode == "once") {
fun(...)
} else if (run_mode == "while") {
counter <- 0
while(counter < 3) {
# Goal: keep ellipsis value for `id` but *update* value for `at`
dots <- rlang::dots_list(...)
if ("at" %in% names(dots)) {
message("`at` was passed via ellipsis:")
message(dots$at)
dots$at <- dots$at + 60
} else {
dots$at <- Sys.time() + 60
}
do.call(fun, dots)
counter <- counter + 1
}
}
}
这是输出:
runtime_gateway()
#> id_a: 2020-02-21 14:22:07
runtime_gateway(at = lubridate::ymd_hms("2020-02-21 10:30:00"))
#> id_a: 2020-02-21 10:30:00
runtime_gateway(run_mode = "while")
#> id_a: 2020-02-21 14:23:09
#> id_a: 2020-02-21 14:23:10
#> id_a: 2020-02-21 14:23:11
runtime_gateway(run_mode = "while", id = "id_b")
#> id_b: 2020-02-21 14:23:12
#> id_b: 2020-02-21 14:23:13
#> id_b: 2020-02-21 14:23:14
runtime_gateway(run_mode = "while", at = lubridate::ymd_hms("2020-02-21 10:30:00"))
#> `at` was passed via ellipsis:
#> 2020-02-21 10:30:00
#> id_a: 2020-02-21 10:31:00
#> `at` was passed via ellipsis:
#> 2020-02-21 10:30:00
#> id_a: 2020-02-21 10:31:00
#> `at` was passed via ellipsis:
#> 2020-02-21 10:30:00
#> id_a: 2020-02-21 10:31:00
由reprex package于2020年2月21日创建(v0.3.0)
关于r - 更新R中三点省略号的值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60338114/