R中的jsonlite :: toJSON太多`[]`括号 - 拆箱json答案

【问题标题】：jsonlite::toJSON too many `[]` brackets in R - unbox jsonR中的jsonlite :: toJSON太多`[]`括号 - 拆箱json
【发布时间】：2018-10-19 11:59:25
【问题描述】：

我目前正在构建一个包含多层信息的 api。目前我正在使用小标题并将信息嵌套在列下：

# A tibble: 1 x 3
  APICallTimeGMT      Error                some_data       
  <dttm>              <list>               <list>          
1 2018-10-19 11:43:10 <data.frame [1 × 2]> <tibble [2 × 3]>

当我使用jsonlite::toJSON 将其转换为JSON 时，我会得到很多列表[] 括号。有没有办法将这些特定对象转换为 json 对象而不是列表。那么，嵌套对象应该是什么类（而不是 data.frame）？

当前输出：

期望的输出：

这里是dput(x) 用于重现性：

structure(list(APICallTimeGMT = structure(1539949390.26164, class = c("POSIXct", 
"POSIXt")), Error = list(structure(list(msg = structure(1L, .Label = "OK", class = "factor"), 
    status = 200), .Names = c("msg", "status"), row.names = c(NA, 
-1L), class = "data.frame")), some_data = list(structure(list(
    Outcome = c("Case1", "Case2"), predictions = list(structure(list(
        ClassA = 0.4, ClassB = 0.1, ClassC = 0.5), .Names = c("ClassA", 
    "ClassB", "ClassC"), row.names = c(NA, -1L), class = "data.frame"), 
        structure(list(ClassA = 0.4, ClassB = 0.1, ClassC = 0.5), .Names = c("ClassA", 
        "ClassB", "ClassC"), row.names = c(NA, -1L), class = "data.frame")), 
    meta = list(structure(list(model = structure(1L, .Label = "Awesome AI", class = "factor"), 
        runs = 55), .Names = c("model", "runs"), row.names = c(NA, 
    -1L), class = "data.frame"), structure(list(model = structure(1L, .Label = "Awesome AI", class = "factor"), 
        runs = 55), .Names = c("model", "runs"), row.names = c(NA, 
    -1L), class = "data.frame"))), row.names = c(NA, -2L), class = c("tbl_df", 
"tbl", "data.frame"), .Names = c("Outcome", "predictions", "meta"
)))), row.names = c(NA, -1L), .Names = c("APICallTimeGMT", "Error", 
"some_data"), class = c("tbl_df", "tbl", "data.frame"))

【问题讨论】：

标签： r tibble jsonlite

【解决方案1】：

Stéphane Laurent 的回答很接近。问题似乎在于，如果数据在嵌套的小标题中，auto-unbox = TRUE 会以某种方式失败。为了正确打印上面的数据，我使用了mutate + purrr：

library(jsonlite)

x_unboxed <- x %>% 
  mutate(Error = map(Error, ~.x %>% unbox),
         some_data = map(some_data, ~.x %>% 
                           mutate(predictions = map(predictions, ~.x %>% unbox),
                                  meta = map(meta, ~.x %>% unbox)))) %>% 
  unbox

x_unboxed %>% toJSON(., pretty = T)

【讨论】：

不错，您找到了解决方案。我刚刚写了一个丑陋的解决方案（将每个数据帧转换为一个列表），但现在不需要发布它。我不知道unbox 函数。