是否可以为包含 ...的一组签名参数定义方法（与...的完全相对）？它不可能＆＃34;开箱即用＆＃34;但理论上它可能（涉及一些调整）或者这是根本不可能的事情由于S4机制的设计方式完成了吗？
我正在寻找符合
的内容setGeneric(
name = "foo",
signature = c("x", "..."),
def = function(x, ...) standardGeneric("foo")
)
setMethod(
f = "foo",
signature = signature(x = "character", "..." = "ThreedotsRelevantForMe"),
definition = function(x, ...) bar(x = x)
)
Martin Morgan感谢地向我指出了dotsMethods并且它说：
目前，“...”不能与其他正式参数混合使用：通用函数的签名只是“...”，或者它不包含“...”。 （此限制可能会在将来的版本中解除。）
考虑以下尝试来概括基于...的调度机制来自一个简单的情况（只有一个更多的函数应该使用通过...传递的参数;例如在...中使用plot()将参数传递给par()）到涉及以下方面的场景（取自here）：
r，收件人，c 调用堆栈的不同层时 另请注意，尽管这样做确实是一种好习惯，但顶级函数/接口不一定需要关注定义（很多）随后调用函数/接口的显式参数，以便正确传递参数。 IMO，这个选择应留给开发人员，因为有时一个或另一个选择更有意义。
如果我可以替换当前通过withThreedots()（AFAICT需要涉及... 的实际拆分）处理的调度，那将会很酷S4调度员不知何故，因此理想情况下只需在foo(x = x, ...)中拨打withThreedots("foo", x = x, ...)而不是foobar()：
withThreedots <- function(fun, ...) {
threedots <- list(...)
idx <- which(names(threedots) %in% sprintf("args_%s", fun))
eval(substitute(
do.call(FUN, c(THREE_THIS, THREE_REST)),
list(
FUN = as.name(fun),
THREE_THIS = if (length(idx)) threedots[[idx]],
THREE_REST = if (length(idx)) threedots[-idx] else threedots
)
))
}
foobar <- function(x, ...) {
withThreedots("foo", x = x, ...)
}
foo <- function(x = x, y = "some text", ...) {
message("foo/y")
print(y)
withThreedots("bar", x = x, ...)
}
bar <- function(x = x, y = 1, ...) {
message("bar/y")
print(y)
withThreedots("downTheLine", x = x, ...)
}
downTheLine <- function(x = x, y = list(), ...) {
message("downTheLine/y")
print(y)
}
foobar(x = 10)
foobar(x = 10, args_foo = list(y = "hello world!"))
foobar(x = 10, args_bar = list(y = 10))
foobar(x = 10, args_downTheLine = list(y = list(a = TRUE)))
foobar(x = 10,
args_foo = list(y = "hello world!"),
args_bar = list(y = 10),
args_downTheLine = list(y = list(a = TRUE))
)
# foo/y
# [1] "hello world!"
# bar/y
# [1] 10
# downTheLine/y
# $a
# [1] TRUE
我想我正在寻找类似的东西：
解释
setGeneric(
name = "foobar",
signature = c("x"),
def = function(x, ...) standardGeneric("foobar")
)
setMethod(
f = "foobar",
signature = signature(x = "ANY"),
definition = function(x, ...) pkg.foo::foo(x = x, ...)
)
假设：foo()在包/名称空间pkg.foo中定义
setGeneric(
name = "foo",
signature = c("x", "y", "..."),
def = function(x, y = "some text", ...) standardGeneric("foo")
)
setMethod(
f = "foo",
signature = signature(x = "ANY", y = "character", "..." = "Threedots.pkg.foo.foo"),
definition = function(x, y, ...) {
message("foo/y")
print(y)
pkg.bar::bar(x = x, ...)
}
)
假设：bar()在包/名称空间pkg.bar中定义：
setGeneric(
name = "bar",
signature = c("x", "y", "..."),
def = function(x, y = 1, ...) standardGeneric("bar")
)
setMethod(
f = "bar",
signature = signature(x = "ANY", y = "numeric", "..." = "Threedots.pkg.bar.bar"),
definition = function(x, y, ...) {
message("bar/y")
print(y)
pkg.a::downTheLine(x = x, ...)
)
setGeneric(
name = "downTheLine",
signature = c("x", "y", "..."),
def = function(x, y = list(), ...) standardGeneric("downTheLine")
)
假设：downTheLine()在包/名称空间pkg.a中定义：
setMethod(
f = "downTheLine",
signature = signature(x = "ANY", y = "list", "..." = "Threedots.pkg.a.downTheLine"),
definition = function(x, y, ...) {
message("downTheLine/y")
print(y)
return(TRUE)
)
说明调度员需要做什么
关键部分是它必须能够区分...中与被调用的相应当前 fun相关的元素（基于常规 和 threedots 签名参数上的完整S4调度）以及应传递给fun可能<的函数的那些元素em>调用（即更新状态为...;类似于上面withThreedots()内发生的事情）：
s4Dispatcher <- function(fun, ...) {
threedots <- splitThreedots(list(...))
## --> automatically split `...`:
## 1) into those arguments that are part of the signature list of `fun`
## 2) remaining part: everything that is not part of
## the signature list and that should thus be passed further along as an
## updated version of the original `...`
args_this <- threedots$this
## --> actual argument set relevant for the actual call to `fun`
threedots <- threedots$threedots
## --> updated `...` to be passed along to other functions
mthd <- selectMethod(fun, signature = inferSignature(args_this))
## --> `inferSignature()` would need to be able to infer the correct
## signature vector to be passed to `selectMethod()` from `args_this`
## Actual call //
do.call(mthd, c(args_this, threedots))
}
这里是一个关于＆＃34;键入三点参数容器＆＃34;的生成器的说明。看起来像。
请注意，为了使这样的机制跨包工作，可能有意义也可以说明某个函数的命名空间（arg ns和字段.ns）：
require("R6")
Threedots <- function(..., fun, ns = NULL) {
name <- if (!is.null(ns)) sprintf("Threedots.%s.%s", ns, fun) else
sprintf("Threedots.%s", fun)
eval(substitute({
INSTANCE <- R6Class(CLASS,
portable = TRUE,
public = list(
.args = "list", ## Argument list
.fun = "character", ## Function name
.ns = "character", ## Namespace of function
initialize = function(..., fun, ns = NULL) {
self$.fun <- fun
self$.ns <- ns
self$.args <- structure(list(), names = character())
value <- list(...)
if (length(value)) {
self$.args <- value
}
}
)
)
INSTANCE$new(..., fun = fun, ns = ns)
},
list(CLASS = name, INSTANCE = as.name(name))
))
}
实施例
x <- Threedots(y = "hello world!", fun = "foo", ns = "pkg.foo")
x
# <Threedots.pkg.foo.foo>
# Public:
# .args: list
# .fun: foo
# .ns: pkg.foo
# initialize: function
class(x)
# [1] "Threedots.pkg.foo.foo" "R6"
x$.args
# $y
# [1] "hello world!"
实际调用将如下所示：
foobar(x = 10)
foobar(x = 10, Threedots(y = "hello world!", fun = "foo", ns = "pkg.foo"))
foobar(x = 10, Threedots(y = 10, fun = "bar", ns = "pkg.bar"))
foobar(x = 10, Threedots(y = list(a = TRUE), fun = "downTheLine", ns = "pkg.a")))
foobar(x = 10,
Threedots(y = "hello world!", fun = "foo", ns = "pkg.foo"),
Threedots(y = 10, fun = "bar", ns = "pkg.bar),
Threedots(y = list(a = 10), fun = "downTheLine", ns = "pkg.a")
)
答案 0 :(得分：6)
请参阅?setGeneric并搜索“...”，然后搜索?dotsMethods。可以定义一个在...上调度的泛型（仅与其他参数不混合以进行调度）。
.A = setClass("A", contains="numeric")
.B = setClass("B", contains="A")
setGeneric("foo", function(...) standardGeneric("foo"))
setMethod("foo", "A", function(...) "foo,A-method")
setGeneric("bar", function(..., verbose=TRUE) standardGeneric("bar"),
signature="...")
setMethod("bar", "A", function(..., verbose=TRUE) if (verbose) "bar,A-method")
导致
> foo(.A(), .B())
[1] "foo,A-method"
> bar(.A(), .B())
[1] "bar,A-method"
> bar(.A(), .B(), verbose=FALSE)
>
我不知道这是否适合您的其他情况。