I have a JSON string with array as the following:
{
"cars": {
"Nissan": [
{"model":"Sentra", "doors":4},
{"model":"Maxima", "doors":4}
],
"Ford": [
{"model":"Taurus", "doors":4},
{"model":"Escort", "doors":2}
]
}
}
I would like to edit a new card brand, using circe at scala.
Instead of
"Nissan": [
{"model":"Sentra", "doors":4},
{"model":"Maxima", "doors":4},
]
I would like to have as a result:
"Nissan": [
{"model":"Sentra", "doors":1000},
],
Thanks.
Made after reading the manual, please do the same next time!
Apart from your JSON being invalid (Trailing comma on object in array "Nissan"
), it should look something like this:
import cats.syntax.either._
import io.circe._, io.circe.parser._
val json: String = """
{
"cars": {
"Nissan": [
{"model":"Sentra", "doors":4},
{"model":"Maxima", "doors":4}
],
"Ford": [
{"model":"Taurus", "doors":4},
{"model":"Escort", "doors":2}
]
}
}
"""
val newJson = parse(json).toOption
.flatMap { doc =>
doc.hcursor
.downField("cars")
.downField("Nissan")
.withFocus(_ =>
Json.arr(
Json.fromFields(
Seq(
("model", Json.fromString("Sentra")),
("doors", Json.fromInt(1000))
)
)
)
)
.top
}
newJson match {
case Some(v) => println(v.toString)
case None => println("Failure!")
}
Try it out! (Rerun to see correct indentation!)
newJson
is actually an Option
, so if parsing or modifying fails, you will get None
.
Calling toOption
on parse(json)
converts the returned Either[Json]
(parsing succeeded / failed) to an Option[Json]
.
We need to use an Option[Json]
in the first place because .top
returns a Option[Json]
(modifying succeeded / failed), too.
This way we can flatMap
and don't have to deal with any nested types (see here).