When handling nested JSON structures, it’s not entirely straightforward since the example don’t offer too much context in regards to handling this. We already know that a Reads converter needs a corresponding model.

{
   "name": "Brandon",
   "age": 75,
   "sex": "male"
}

case class Human(name: Stringge: Int, sex: String)

// Builder
val humanReads: Reads[Human] = (
    (__ \ "name").read[String] and
    (__ \ "age").read[Int] and
    (__ \ "sex").read[String]
)(Human.apply _)

But what if have a JSON structure contains a sequence or list of other Objects like children? Simple…

{
   "name": "Brandon",
   "age": 75,
   "sex": "male",
   "children": [
      {
         "name": "Emily",
         "age": 45,
         "sex": "female",
       },
       {
        "name": "Sam",
        "age": 42,
        "sex": "male",
       }
   ]
}

case class Human(name: String, "age": Int, sex: String, children: Option[List[Human]])

// Builder
implicit val humanReads: Reads[Human] = (
    (__ \ "age").read[Int] and
    (__ \ "sex").read[String] and
    (__ \ "chilidren).readNullable[List[Human]]
)(Human.apply _)

Just wrap it as an “optional” list with a Human type. However, this only represents one level deep. What if you wanted to create a family tree based on a loaded JSON structure? Fear not, this is where lazyRead and lazyWrites comes into play!

In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed. It is a kind of lazy evaluation that refers specifically to the instantiation of objects or other resources.

These lazy methods to handle these recursions without affecting performance of modeling a structure until it’s finally needed. To use this, we apply a lazyRead or lazyWrite to our Builder or Reader to inform the builder apply the reader upon this property.

{
   "name": "Brandon",
   "age": 85,
   "sex": "male",
   "children": [
      {
         "name": "Emily",
         "age": 45,
         "sex": "female",
       },
       {
        "name": "Sam",
        "age": 52,
        "sex": "male",
        "children": [
           {
              "name": "Sona",
              "age": 30,
              "sex": "female",
              "children": [
                 {
                    "name": "Tom",
                    "age": 1,
                    "sex": "male"
                 }
              ]
            }
        ]
       }
   ]
}

case class Human("age": Int, sex: String, "children": Option[List[Human]])

// Builder
implicit val humanReads: Reads[Human] = (
    (__ \ "age").read[Int] and
    (__ \ "sex").read[String] and
    (__ \ "chilidren").lazyReadullable[Reads.list[Human]](humanReads)
)(Human.apply _)

Viola!