Nested JSON

[richard-churchman]

Hello,

I started with Plumber today and it is working great. When the JSON is flat, it works exactly as expected.

How does Plumber deal with JSON that is nested and multi-layered? How would I craft the function in this manner?

Am I to understand that I have to flatten the structure before i send it over?

Thanks

[shrektan]

I don't understand what you mean. There's no difference between flat JSON and multi-layered JSON, in my opinion. An example may help to understand.

[freitasskeeled]

I was about to ask the same question (I think) so I decided to comment here.

In my case, the application requires that the fromJSON call has the flatten flag set to TRUE. Using Plumber, I'm unable to use the parsed args directly because there is no way to specify that. Alternatively, I use req$postBody with my own parsing.

I checked the code and it seems that there is not way to configure that. safeFromJSON function accepts args that are then passed to jsonlite::fromJSON call but the parseBody function doesn't take advantage of that.

Maybe adding a way to set custom settings for the default filters?

[schloerke]

Closing due to inactivity

As a note, plumber can parse any valid JSON structure and can also return very complicated JSON structures.

[mrkaye97]

@schloerke I just stumbled upon this issue and I think I'm having the same problem. Here's what I want to be able to do:

#* @param bar
#* @post /foo
foo <- function(bar) {
  bar
}

and be able to make requests to that endpoint like this:

POST(
  "<< some url >>/foo"
  body = list(
    baz = list(
      bar = "abc",
      qux = 123
    ) %>% toJSON()
  )
)

but it appears (at least AFAICT) that in order to be able to use nesting like that, I'll need to parse the JSON myself. Is there a best practice for how to deal with nested json like this? I'd almost like to be able to do something like #* @param baz$bar or similar, but I don't know enough about the internals to know if that'd be possible

[meztez]

Plumber will parse your json input and do a named argument matching only for the top level elements (non nested) via an R do.call.

More detailed

It does a do.call with your handler function foo and args produced by the parser. JSON parser args are top level elements.
do.call :

plumber/R/plumber-step.R

Line 84 in 20c7d9f

do.call(private$func, relevant_args, envir = private$envir)

json parser :

plumber/R/parse-body.R

Line 383 in 28bc58c

parser_json <- function(...) {

safeFromJson method : https://github.com/rstudio/plumber/blob/master/R/json.R

If this is not enough, you could write your own parser as it is relatively easy to extend.

https://www.rplumber.io/reference/register_parser.html

#* @param baz
#* @post /foo
function(baz) {
  baz$bar
}

[mrkaye97]

@meztez Aha, gotcha with the updated comment. Thanks!