Question

I am writing some helper functions to convert my R variables to JSON. I’ve come across this problem: I would like my values to be represented as JSON arrays, this can be done using the AsIs class according to the RJSONIO documentation.

x = "HELLO"
toJSON(list(x = I(x)), collapse="")

"{ \"x\": [ \"HELLO\" ] }"

But say we have a list

y = list(a = "HELLO", b = "WORLD")
toJSON(list(y = I(y)), collapse="")

"{ \"y\": {\n \"a\": \"HELLO\",\n\"b\": \"WORLD\" \n} }"

The value found in y -> a is NOT represented as an array. Ideally I would have

"{ \"y\": [{\n \"a\": \"HELLO\",\n\"b\": \"WORLD\" \n}] }"

Note the square brackets. Also I would like to get rid of all “\n”s, but collapse does not eliminate the line breaks in nested JSON. Any ideas?

Answer 1

try writing as

y = list(list(a = "HELLO", b = "WORLD"))
test<-toJSON(list(y = I(y)), collapse="")

when you write to file it appears as:

{ "y": [
 {
 "a": "HELLO",
"b": "WORLD" 
} 
] }

I guess you could remove the \n as

test<-gsub("\n","",test)

or use RJSON package

> rjson::toJSON(list(y = I(y)))
[1] "{\"y\":[{\"a\":\"HELLO\",\"b\":\"WORLD\"}]}"

The reason

> names(list(a = "HELLO", b = "WORLD"))
[1] "a" "b"
> names(list(list(a = "HELLO", b = "WORLD")))
NULL

examining the rjson::toJSON you will find this snippet of code

  if (!is.null(names(x))) 
            return(toJSON(as.list(x)))
        str = "["

so it would appear to need an unnamed list to treat it as a JSON array. Maybe RJSONIO is similar.