[2.0] concatenating JSValues

[danielkol]

So I currently am able to implicitly convert a single object to Json using the Play Framework libraries.  The following is an example of definitions for two of them.

  implicit object UserFormat extends Format[User] {

    def reads(json: JsValue): User = User(

      (json \ "id").asInstanceOf[Pk[Long]],

      (json \ "email").as[String])

    def writes(u: User): JsValue = JsObject(List(

      "id" -> JsInteger(u.id.get),

      "email" -> JsString(u.email)

    ))

  }

implicit object GroupFormat extends Format[UserGroup] {

  def reads(json: JsValue): UserGroup = UserGroup(

    (json \ "userId").as[Long],

    (json \ "groupId").as[Long],

    (json \ "groupName").as[String]

  )

  def writes(ug: UserGroup): JsValue = JsObject(List(

    "userId" -> JsInteger(ug.userId),

    "groupId" -> JsNumber(ug.groupId),

    "groupName" -> JsBoolean(ug.groupNamel)

  ))

}

So currently in my code I can define

toJson(someUser)

and

toJson(someUserGroup)

Is there an easy way to define an implicit formatter for a type (User, UserGroup) for writing so I can implicitly call:

toJson((SomeUser, SomeUserGroup))

I ideally want to be able to call something like the following write def below (Obviously the + operator doesn't work in the following example)

  implicit object UserWithUserGroupFormat extends Format[(User, UserGroup)] {

    def reads(json: JsValue): ...

    def writes(uug: (User, UserGroup)): JsValue = toJson(uug._1) + toJson(uug._2)

  }

[Pascal Voitot Dev]

See below

Yes it should be possible.

you can merge 2 JsObject:

toJson(someUser) ++ toJson(someUserGroup)

But merging User and UserGroup in the same object seems weird to me...

maybe you want to write

JsObject(Seq(
  ("user", toJson(someUser)),
  ("group", toJson(someUserGroup))

))
 
regards
pascal

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[Derek Williams]

On Wed, Mar 7, 2012 at 4:32 PM, danielkol <dko...@toclarity.com> wrote:

Is there an easy way to define an implicit formatter for a type (User, UserGroup) for writing so I can implicitly call:

toJson((SomeUser, SomeUserGroup))

I ideally want to be able to call something like the following write def below (Obviously the + operator doesn't work in the following example)

  implicit object UserWithUserGroupFormat extends Format[(User, UserGroup)] {

    def reads(json: JsValue): ...

    def writes(uug: (User, UserGroup)): JsValue = toJson(uug._1) + toJson(uug._2)

  }

JsObject contains the '++' method for merging two objects together:

https://github.com/playframework/Play20/blob/master/framework/src/play/src/main/scala/play/api/libs/json/JsValue.scala#L167

So then you should be able to do something like this (untested):

implicit def mergeWrites[A: JsonFormat, B: JsonFormat]: Writes[(A, B)] = new Writes[(A, B)] {

  def writes(pair: (A, B)): JsValue = toJson(pair._1).as[JsObject] ++ toJson(pair._2).as[JsObject]

}

Or make a non generic version:

impicit object UserWithUserGroupWrites extends Writes[(User, UserGroup)] {

  def writes(pair: (User, UserGroup)): JsValue = toJson(pair._1).as[JsObject] ++ toJson(pair._2).as[JsObject]

}

You will end up with both 'id' and 'userId' in your json of course

--

Derek Williams

[Pascal Voitot Dev]

yes you're right: I forgot the ".as[JsObject]" ;)

Pascal

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