Converting R list to JSON

Question

A simple question - I'd like to convert a list to JSON in R. Let's say this is my list:

listtest = list(
  list(section_id = NULL, name = 'name1', slug = 'slug1'),
  list(section_id = NULL, name = 'name2', slug = 'slug2'),
  list(section_id = NULL, name = 'name3', slug = 'slug3', categories = 
         list(
           list(section_id = NULL, name = 'name31', slug = 'slug31'),
           list(section_id = NULL, name = 'name32', slug = 'slug32')
         )
  )
)

So I use a simple

jsontest = toJSON(listtest, pretty = TRUE, auto_unbox = TRUE)

Then I get a JSON like this:

[
  {
    "section_id": {},
    "name": "name1",
    "slug": "slug1"
  },
  {
    "section_id": {},
    "name": "name2",
    "slug": "slug2"
  },
  {
    "section_id": {},
    "name": "name3",
    "slug": "slug3",
    "categories": [
      {
        "section_id": {},
        "name": "name31",
        "slug": "slug31"
      },
      {
        "section_id": {},
        "name": "name32",
        "slug": "slug32"
      }
    ]
  }
] 

However, at the beginning and end of the code I get '[' and ']'. How can I get rid of this? When uploading to mongoDB it gives me an error whereas without the brackets it works fine.

Answer 1

Use gsub()

jsontest <- gsub(pattern = '^\[', replacement = "", x = jsontest)
jsontest <- gsub(pattern = '\]$', replacement = "", x = jsontest)

Results :

  {
    "section_id": {},
    "name": "name1",
    "slug": "slug1"
  },
  {
    "section_id": {},
    "name": "name2",
    "slug": "slug2"
  },
  {
    "section_id": {},
    "name": "name3",
    "slug": "slug3",
    "categories": [
      {
        "section_id": {},
        "name": "name31",
        "slug": "slug31"
      },
      {
        "section_id": {},
        "name": "name32",
        "slug": "slug32"
      }
    ]
  }

Still json class :

> class(jsontest)
[1] "json"

But maybe the blank space might cause some troubles.

Answer 2

Using the mongolite package you should be able to simply use the insert() function to insert it directly into the collection.