在 R 中，如何知道 function 在返回之前是否向控制台打印了警告消息？

Question

func <- function() {
  warning("warning message")
  return(1)
}

1. func will print a warning before returning. But how can the fact that it print warning be detected by code?
2. How can the warning message be captured as a character value?

Answer 1

You can wrap a call to the function with tryCatch to catch warnings. For example you can do it around the function itself

x <- tryCatch(func(), warning= function(w) {
  message(paste("a warning did occur:", conditionMessage(w)))
  return(0)
})
x

or you could do it inside the function

func <- function() {
  tryCatch({
    warning("warning message")  
  }, warning = function(w) {
    message(paste("a warning did occur:", conditionMessage(w)))
  })
  return(1)
}