Circe-Optics如何使用破折号指定路径

import io.circe._
import io.circe.parser._

val jsonStr = """
{
  "name": "John",
  "age": 30,
  "address": {
    "city": "New York",
    "country": "USA"
  }
}
"""

val json = parse(jsonStr).getOrElse(Json.Null)

val name = json.hcursor.downField("name").as[String].getOrElse("")
val age = json.hcursor.downField("age").as[Int].getOrElse(0)
val city = json.hcursor.downField("address").downField("city").as[String].getOrElse("")
val country = json.hcursor.downField("address").downField("country").as[String].getOrElse("")

println(s"Name: $name")
println(s"Age: $age")
println(s"City: $city")
println(s"Country: $country")

Name: John
Age: 30
City: New York
Country: USA

import io.circe.syntax._

val updatedJson = json.hcursor.downField("name").withFocus(_.mapString(_ => "Jane")).top.getOrElse(Json.Null)

println(updatedJson.noSpaces)

{"name":"Jane","age":30,"address":{"city":"New York","country":"USA"}}