Play Framework 2.1.1 Json Writes nested objects - json

Question

I've been trying to get my head around this all afternoon to no avail, Play 2.1.1 overhauled how the Json reads and writes work.
Basically I have a wrapper object that looks like:
case class CombinedUser(user: SocialUser, userdetails: UserDetails)
as you can see it contains 2 classes that I want to serialize and deserialize to json.
But I don't understand how I can get and set the fields in the subclasses using the new design.
For example
implicit val combinedUser2Reads = (
(__ \ "email").read[String] and
(__ \ "providerid").read[String] and
(__ \ "firstname").read[String] and
(__ \ "lastname").read[String] and
(__ \ "fullname").read[String] and
(__ \ "avatarurl").read[String] and
(__ \ "address1").read[String] and
(__ \ "address2").read[String] and
(__ \ "address3").read[String] and
(__ \ "city").read[String] and
(__ \ "country").read[String] and
(__ \ "phone").read[String] and
(__ \ "publickey").as[String]
)(CombinedUser2.apply _)
I want a json blob that has most of the subclasses fields, all strings.
Because it uses the apply stuff, I don't see how I can create the subclasses before the mapping.
Any help or guidance is much appreciated.
Thanks
Tom

Answer 1

You can do it this way:
case class SocialUser(firstName: String, lastName: String)
case class UserDetails(avatarUrl: String, phone: String)
case class CombinedUser(user: SocialUser, userDetails: UserDetails)
implicit val combinedUserReads: Reads[CombinedUser] = (
(__ \ "user").read((
(__ \ "firstName").read[String] and
(__ \ "lastName").read[String]
)(SocialUser)) and
(__ \ "userDetails").read((
(__ \ "avatarUrl").read[String] and
(__ \ "phone").read[String]
)(UserDetails))
)(CombinedUser)
However its better to create separated Reads:
implicit val socialUserReads = (
(__ \ "firstName").read[String] and
(__ \ "lastName").read[String]
)(SocialUser)
implicit val userDetailsReads = (
(__ \ "avatarUrl").read[String] and
(__ \ "phone").read[String]
)(UserDetails)
implicit val combinedUserReads: Reads[CombinedUser] = (
(__ \ "user").read[SocialUser] and
(__ \ "userDetails").read[UserDetails]
)(CombinedUser)
Edit: for simple case classes, its possible to do:
implicit val socialUserReads = Json.format[SocialUser]
implicit val userDetailsReads = Json.format[UserDetails]
implicit val combinedUserReads = Json.format[CombinedUser]
Here is quite comprehensive introduction to JSON Reads and more.
How about partial objects? If I don't want to fill in every field in
the constructor, can I pass empties or do I overload the constructor
or similar?
Use Option:
case class CombinedUser(user: SocialUser, userDetails: Option[UserDetails])
//reads
implicit val combinedUserReads: Reads[CombinedUser] = (
(__ \ "user").read[SocialUser] and
(__ \ "userDetails").readOpt[UserDetails]
)(CombinedUser)
//writes
implicit val combinedUserWrites: Writes[CombinedUser] = (
//socialUserWrites and userDetailsWrites must be in scope
(__ \ "user").write[SocialUser] and
(__ \ "userDetails").write[Option[UserDetails]]
)(unlift(CombinedUser.unapply))
val json = Json.obj(
"user" -> Json.obj(
"firstName" -> "Homer",
"lastName" -> "Simpson"
)
)
Json.fromJson[CombinedUser](json)
//JsSuccess(CombinedUser(SocialUser(Homer,Simpson),None),)