R - Create JSON for Adobe Analytics API call - define object conditionally - json

Question

I have following code to create a JSON for making a call to Adobe Analytics API (method segment.save)
item <-
list(definition = list(
container = list (
type = "hits",
operator = "or",
rules=I(list(
list(value= "test1 test2",
operator = "contains_any",
element = "page")))
)
),
owner="test",
reportSuiteID="test",
description="API Generated Segment",
name="test segment"
)
Once prettyfied and auto-unboxed, the result is:
> jsonlite::toJSON(item, pretty = T, auto_unbox= T)
{
"definition": {
"container": {
"type": "hits",
"operator": "or",
"rules": [
{
"value": "test1 test2",
"operator": "contains_any",
"element": "page"
}
]
}
},
"owner": "test",
"reportSuiteID": "test",
"description": "API Generated Segment",
"name": "test segment"
}
Good for creating new segments, but not so good for editing them
The JSON structure is valid, as I am able to create the new segment. However, I would like to check if the segment already exists (using f.i. the GetSegments() function from randyzwitch RSiteCatalyst package and check if name coincides already with a created segment). If the segment already exists, I want to pass the id to the API call, which is the method used for editing already existing segments. It should then look like:
> jsonlite::toJSON(item, pretty = T, auto_unbox= T)
{
"definition": {
...
},
"owner": "test",
"reportSuiteID": "test",
"description": "API Generated Segment",
"name": "test segment",
"id": "s1982XXXXXXXXX_XXXXX_XXXXX",
}
It is possible to make an if alike statement within the list() definition provided in the first piece of code? I would like to reach a solution that does not need an if statement that checks if segmentID exists and, depending on it, generates a call with id or a call without id.

Answer 1

Once a "JSON alike structure" is created using list function:
item <-
list(definition = list(
container = list (
type = "hits",
operator = "or",
rules=I(list(
list(value= "test1 test2",
operator = "contains_any",
element = "page")))
)
),
owner="test",
reportSuiteID="test",
description="API Generated Segment",
name="test segment"
)
We can push new elements to this list using the needed conditions. For example, if we have our segment IDs in a dataframe with name segments, we can push this ID to item this way:
if (!is.na(segments$segmentID[i])) {
item <- c(item, id=segments$segmentID[i])
}