使用 tryCatch() 将错误和警告存储在列表中

Question

我编写了一段代码，用于从 API 中提取 JSON 数据并将其转换为数据框。基本代码是：

hospitals_url <- "https://services1.arcgis.com/Hp6G80Pky0om7QvQ/arcgis/rest/services/Hospitals_1/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=4326&f=json"
        hospitals_num <- c(0, 2000, 4000, 6000)
        hosget <- lapply(hospitals_num, function(num) {
          hospitals_url_loop <- paste(hospitals_url, "&resultOffset=", num)
          hospitals_json <- fromJSON(hospitals_url_loop)
          hospitals_df <- as.data.frame(hospitals_json$features$attributes)})
        
        hospitals_df <- do.call(rbind, hosget)}

我正在尝试将其添加到 tryCatch() 函数中，以便我可以更多地参与错误管理和控制。我要做的是使用tryCatch() 函数的错误和警告部分来创建包含错误（如果有的话）的变量，并将它们放入列表中。我有以下内容：

tryCatch({
        hospitals_url <- "https://services1.arcgis.com/Hp6G80Pky0om7QvQ/arcgis/rest/services/Hospitals_1/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=4326&f=json"
        hospitals_num <- c(0, 2000, 4000, 6000)
        hosget <- lapply(hospitals_num, function(num) {
          hospitals_url_loop <- paste(hospitals_url, "&resultOffset=", num)
          hospitals_json <- fromJSON(hospitals_url_loop)
          hospitals_df <- as.data.frame(hospitals_json$features$attributes)})
        
        hospitals_df <- do.call(rbind, hosget)},
      
      error = function(hosp_e){
              hosp_e <- simpleError("Error: Hospital data has not been collected due to an error. Please ensure that the number loop is correct.")
              print(hosp_e)},
      
      warning = function(hosp_w){
              hosp_w <- simpleWarning("Warning: Hospital data has not been collected. Please ensure that the number loop is correct.")
              print(hosp_w)},
        
      finally = {
              hospitals_log <- (paste("Hospitals Code Has Been Executed on ", Sys.Date()))
              hosp_error <- if (exists("hosp_e") == FALSE) {
                      ("No Error")}
              hosp_warning <- if (exists("hosp_w") == FALSE) {
                      ("No Warning")}
              print(paste(hospitals_log, ", ", hosp_error, ", ", hosp_warning))
              hospitals_output = list(hospitals_log, hosp_error, hosp_warning, paste("URL: ", hospitals_url))
              rm(hospitals_log, hosp_warning, hosp_error, hospitals_num, hosget, hospitals_url)
                })

当我创建一个错误（例如，向 hospital_url 添加一个额外的“l”）时，我的 simpleerror 会打印出 (<simpleError: Error: Hospital data has not been collected due to an error. Please ensure that the number loop is correct.>)，但不会存储为变量并添加到列表中。如何更改我的代码来完成此操作？

我查看了以下内容（here 和 here），但现在更加困惑... :(

Answer 1

这是一个将tryCatch 放入循环中并保存生成的错误和警告的版本：

  hospitals_url <- "https://services1.arcgis.com/Hp6G80Pky0om7QvQ/arcgis/rest/services/Hospitals_1/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=4326&f=json"
  hospitals_num <- c(0, 2000, 4000, 6000)
  hosp_e <- list()
  hosp_w <- list()
  
  hosget <- lapply(hospitals_num, function(num) {
    tryCatch({
      hospitals_url_loop <- paste(hospitals_url, "&resultOffset=", num)
      hospitals_json <- fromJSON(hospitals_url_loop)
      hospitals_df <- as.data.frame(hospitals_json$features$attributes)},
      error = function(e){
        hosp_e <<- c(hosp_e, list(e))
        print(e)},
      
      warning = function(w){
        hosp_w <<- c(hosp_w, list(w))
        print(w)}     
      ) })
    
  hospitals_df <- do.call(rbind, hosget)
  

我没有使您的finally 代码适应这种重新排列；我会把它留给你。但最后，hosp_e 将是一个包含所有错误的列表，hosp_w 将是一个包含所有警告的列表。