Get Array out of JSON-structure with tidyjson - r

Question

I'm trying to read an array out of a JSON structure with tidyjson as I'm trying to fasten up my code.
My input data is of the structure
json <- "{\"key1\":\"test\",\"key2\":[\"abc\",\"def\"]}"
I want my output to be a data frame where key1 is one column and key2 is the second column in which all elements of the array are pasted together and separated by ";".
I tried something like
result <- json %>% spread_values(a = jstring("key1"), b = paste0(jstring("key2"), collapse = ";"))
I really have no idea how to get the array out of the JSON in the spread_values function.
I got what I want with
key2 <- json %>% enter_object("key2")
attributes(key2)$JSON %>% unlist() %>% paste0(collapse = ";")
but as I don't have unique keys I can't join it to the rest of my data and I think there must be a better way.

Answer 1

I'm glad you got something working! In case anyone else happens upon this question, there are definitely many ways to accomplish this task!
One is to use tidyjson to gather the data into a tall structure, then summarize:
library(tidyjson)
library(dplyr)
json <- "{\"key1\":\"test\",\"key2\":[\"abc\",\"def\"]}"
myj <- tidyjson::as.tbl_json(json)
myj %>%
# make the data tall
spread_values(key1 = jstring(key1)) %>%
enter_object("key2") %>%
gather_array("idx") %>%
append_values_string("key2") %>%
# now summarize
group_by(key1) %>%
summarize(key2 = paste(key2, collapse = ";"))
#> # A tibble: 1 x 2
#> key1 key2
#> <chr> <chr>
#> 1 test abc;def
Created on 2021-10-29 by the reprex package (v0.3.0)
Another way is to grab the json data directly with json_get_column() and mutate that:
library(tidyjson)
library(dplyr)
json <- "{\"key1\":\"test\",\"key2\":[\"abc\",\"def\"]}"
myj <- tidyjson::as.tbl_json(json)
myj %>%
spread_values(key1 = jstring(key1)) %>%
enter_object("key2") %>%
json_get_column("array") %>%
mutate(key2 = purrr::map_chr(array, ~ paste(.x, collapse = ";"))) %>%
as_tibble() %>% # drop tbl_json structure
select(key1, key2)
#> # A tibble: 1 x 2
#> key1 key2
#> <chr> <chr>
#> 1 test abc;def
Created on 2021-10-29 by the reprex package (v0.3.0)