Question

我有兴趣编写一个基于同一对象的多个类类型运行的通用方法。例如，假设我们有以下内容：

redApple <- function(){
 structure(list(), class = c("apple", "red"))
}

greenApple <- function(){
 structure(list(), class = c("apple", "green"))
}

eat <- function(x)UseMethod("eat")
eat.apple <- function(x)  print("Eating apple")

color <- function(x) UseMethod("color")
color.red <- function(x) print("my food is red")
color.green <- function(x) print("my food is green")

现在我们创建以下对象：

obj1 <- redApple()
obj2 <- greenApple()

这里color(obj1)打印my food is red和color(obj2)打印my food is green，而eat(obj1)和eat(obj2)都打印Eating apple。

现在，我希望我的泛型函数对obj1和obj2的行为有所不同。例如，我希望eat(obj1)打印Eating red apple，而eat(obj2)打印Eating green apple

Answer 1

您可以检查传递给该函数的对象的类并相应地进行大小写：

eat.apple <- function(x)  
{
  if("green" %in% class(x)) print("Eating green apple")
  else if("red" %in% class(x)) print("Eating red apple")
  else print("Eating generic apple!")
}

##addition

eat.green <- function(x)  
{
  print("Eating green apple")
}

eat.red <- function(x)  
{
  print("Eating red apple")
}

具有多个类的对象的泛型函数

1 个答案: