R 将 RSelenium 驱动程序环境作为函数参数传递

我可能没有看到明显的东西，无论如何我想创建函数来自动从远程驱动程序已处理的 URL 中提取文本。我想将 xpath 表达式和可以找到远程驱动程序的环境作为函数参数传递

library(RSelenium)

url="http://stackoverflow.com/search?q=r+program"
remdir<-remoteDriver(remoteServerAddr = "localhost", port = 4444, browserName = "firefox")
remdir$open()
remdir$navigate(url)
env<-environment()

#env should be the environment in wich remdir exist (remdir itself?)
#xp the xpath expression to evaluate in the form "//*"
fun.XpathExtractText<-function(xp,env)
{
  cat("\ncheck if session open\n")
  #look in env for an open session
  if ((eval(quote(is.na(remdir$sessionid)),envir = env)))
    stop("ERROR NO SESSION ID open new one")
  cat("session found\n")
  #accept xpath expression as is
  xp <- substitute(xp)
  txt<-c()
  #build the call to env
  cat("calling\n")
  call<-paste0("remdir$findElements(using = \"xpath\",\"",as.character(xp),"\")")
  tgt<-eval(as.name(call),envir = env)
  cat("Target locked\n")
  txt<-lapply(tgt,function(c){c$getElementText()})
  return(txt)
}

该函数的可能调用可能是fun.XpathExtractText("//*",env)但在调用构建部分之后不久，出现了错误消息：

Error in eval(expr, envir, enclos) : 
 object 'remdir$findElements(using = "xpath","//*")' not found 

但是如果我直接在 env 中执行从错误消息中提取的调用它将起作用。

tgt<-remdir$findElements(using = "xpath","//*")

我尝试将 remdir 本身作为环境传递，因为它是一个环境，但这根本不算数，该函数在调用构建后陷入同一点。 我不知道什么？

不确定你到底想做什么。然而eval似乎没有答案。你应该通过remoteDriver对象到你的函数中：

library(RSelenium)

url="http://stackoverflow.com/search?q=r+program"
remdir<-remoteDriver(remoteServerAddr = "localhost", port = 4444, browserName = "firefox")
remdir$open()
remdir$navigate(url)

fun.XpathExtractText<-function(xp, remdir)
{
  cat("\ncheck if session open\n")
  #look in env for an open session
  if (is.na(remdir$sessionid))
    stop("ERROR NO SESSION ID open new one")
  cat("session found\n")
  #accept xpath expression as is
  cat("calling\n")
  tgt <- remdir$findElements(using = "xpath",as.character(xp))
  cat("Target locked\n")
  txt<-lapply(tgt,function(c){c$getElementText()})
  return(txt)
}