Convert List to Json - json

Question

How do I create a Json (Circe) looking like this:
{
"items": [{
"field1": "somevalue",
"field2": "somevalue2"
},
{
"field1": "abc",
"field2": "123abc"
}]
}
val result = Json.fromFields(List("items" -> ???))

Answer 1

You can do so using Circe's built in list typeclasses for encoding JSON. This code will work:
import io.circe.{Encoder, Json}
import io.circe.syntax._
case class Field(field1: String, field2: String)
object Field {
implicit val encodeFoo: Encoder[Field] = new Encoder[Field] {
final def apply(a: Field): Json = Json.obj(
("field1", Json.fromString(a.field1)),
("field2", Json.fromString(a.field2))
)
}
}
class Encoding(items: List[Field]) {
def getJson: Json = {
Json.obj(
(
"items",
items.asJson
)
)
}
}
If we instantiate an "Encoding" class and call getJson it will give you back the desired JSON. It works because with circe all you need to do to encode a list is provide an encoder for whatever is inside the list. Thus, if we provide an encoder for Field it will encode it inside a list when we call asJson on it.
If we run this:
val items = new Encoding(List(Field("jf", "fj"), Field("jfl", "fjl")))
println(items.getJson)
we get:
{
"items" : [
{
"field1" : "jf",
"field2" : "fj"
},
{
"field1" : "jfl",
"field2" : "fjl"
}
]
}