Adding elements to JSON array using circe and scala - scala

Question

I have a JSON string as the following:
{
"cars": {
"Nissan": [
{"model":"Sentra", "doors":4},
{"model":"Maxima", "doors":4},
{"model":"Skyline", "doors":2}
],
"Ford": [
{"model":"Taurus", "doors":4},
{"model":"Escort", "doors":4}
]
}
}
I would like to add a new cars brand (in addition to Nissan and Ford), using circe at scala.
How could I do it?
Thank you in advance.

Answer 1

You can modify JSON using cursors. One of the possible solutions:
import io.circe._, io.circe.parser._
val cars: String = """
{
"cars": {
"Nissan": [
{"model":"Sentra", "doors":4},
{"model":"Maxima", "doors":4},
{"model":"Skyline", "doors":2}
],
"Ford": [
{"model":"Taurus", "doors":4},
{"model":"Escort", "doors":4}
]
}
}"""
val carsJson = parse(cars).getOrElse(Json.Null)
val teslaJson: Json = parse("""
{
"Tesla": [
{"model":"Model X", "doors":5}
]
}""").getOrElse(Json.Null)
val carsCursor = carsJson.hcursor
val newJson = carsCursor.downField("cars").withFocus(_.deepMerge(teslaJson)).top
Here we just go down to cars field, "focus" on it and pass the function for modifying JSON values. Here deepMerge is used.
newJson will be look as follows:
Some({
"cars" : {
"Tesla" : [
{
"model" : "Model X",
"doors" : 5
}
],
"Nissan" : [
{
"model" : "Sentra",
"doors" : 4
},
{
"model" : "Maxima",
"doors" : 4
},
{
"model" : "Skyline",
"doors" : 2
}
],
"Ford" : [
{
"model" : "Taurus",
"doors" : 4
},
{
"model" : "Escort",
"doors" : 4
}
]
}
})