fromJSON, toJSON, square brackets problem

[baggord]

Hi, I'm mainly working with Python, but I decided to use R Shiny for a webapp project.

I've JSON file, I want to read it, and send to an API via POST request.

Example:

{
  "txt_field": "bar",
  "list_field": ["foo"],
  "list_of_dicts": [{ "a": 42, "b": "b" }],
  "list_of_lists": [[2,1,3,4], [3,4,1,2]]
}

The problem is when I use fromJSON, toJSON functions the output is not the same as the initial JSON. txt_field becomes an array "txt_field": ["bar"].

I'm not good at R but I think this about data types in R. Even the a string is 1 length vector with type character. So, I would like to know the reason behind this and more importantly how do I read the json and pass it to an API without changing the original structure.

[nirgrahamuk]

jsonlite will assume that you dont want to unbox single entry fields,
if you wanted single entries to be unboxed you can use auto_unbox=TRUE param on your toJSON() call.
However, this will unbox list_field 'foo' also...

[baggord]

Thank you. I read that in the documentation too, but as you said it will unbox the other list. So, you are saying there is no way to preserve the actual format?

[nirgrahamuk]

You can do it.
turns out the fromJSON() function has simplifyVector argument that you can use.

for example:

a_json_char <- '{
  "txt_field": "bar",
  "list_field": ["foo"],
  "list_of_dicts": [{ "a": 42, "b": "b" }],
  "list_of_lists": [[2,1,3,4], [3,4,1,2]]
}'

library(jsonlite)

(rdata <- fromJSON(a_json_char,simplifyVector = FALSE))

(toJSON_output <- toJSON(rdata,auto_unbox = TRUE))

min_orig <- minify(a_json_char)
min_new <- minify(toJSON_output)

identical(min_orig,min_new)