Adding elements to JSON array using circe and 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.

Duelist · Accepted Answer · 2018-10-06 16:54:16Z

3

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
      }
    ]
  }
})

edited Oct 6, 2018 at 16:54

answered Oct 6, 2018 at 16:35

Duelist

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1 Comment

Doe Over a year ago

Yeah, that's it. Thank you!

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