依赖其他参数的匹配参数最佳实践

Question

依赖其他参数的匹配参数最佳实践

4

我是 R 函数的新手，到目前为止，我会检查参数，例如：

foo = function(state = c("solid", "liquid"),
               thing = c("rock", "water")) {
  
  state = match.arg(state)
  thing = match.arg(thing)
  
  if (state == "solid" & thing == "water") {
    stop("thing can't be water if state is solid!")
  }
  
  if (state == "liquid" & thing == "rock") {
    stop("thing can't be rock if state is liquid!")
  }
  
}

foo("solid", "brick")
#> Error in match.arg(thing): 'arg' deve ser um dentre "rock", "water"

foo("solid", "water")
#> Error in foo("solid", "water"): thing can't be water if state is solid!

foo("liquid", "rock")
#> Error in foo("liquid", "rock"): thing can't be rock if state is liquid!

^{使用reprex包（v0.3.0）于2020-06-28创建}

但是当处理多个参数时，似乎需要付出很多工作。

我查看了assetthat和checkmate包，但对于正确或标准的做法并不清楚。

- Alberson Miranda

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- r2evans · Accepted Answer

我建议使用“允许列表”（allowlist）或“拒绝列表”（denylist），取决于哪个更短（你将有多少例外情况），但你必须以某种方式硬编码它们。

例如：

foo = function(state = c("solid", "liquid", "both"),
               thing = c("rock", "brick", "water", "either")) {
  
  state = match.arg(state)
  thing = match.arg(thing)

  state_denylist <- list(
    solid = "water",
    liquid = c("rock", "brick")
  )

  if (thing %in% state_denylist[[state]]) {
    stop("thing cannot be ", sQuote(thing), " if state is ", sQuote(state))
  }
 
}

或者，如果定义允许组合更容易，则可以使用state_allowlist并相应地更改您的逻辑（... && ! thing %in% ...）。