r - 如何重试错误语句？

Question

如果语句出错，我怎样才能简单地告诉 R 重试语句几次？例如。我希望做这样的事情:

tryCatch(dbGetQuery(...),           # Query database
    error = function(e) {
        if (is.locking.error(e))    # If database is momentarily locked
            retry(times = 3)        # retry dbGetQuery(...) 3 more times
        else {
            # Handle other errors
        }
    }
)

Answer 1

我通常将 try block 放入循环中，当不再失败或达到最大尝试次数时退出循环。

some_function_that_may_fail <- function() {
  if( runif(1) < .5 ) stop()
  return(1)
}

r <- NULL
attempt <- 1
while( is.null(r) && attempt <= 3 ) {
  attempt <- attempt + 1
  try(
    r <- some_function_that_may_fail()
  )
}