pathikrit / metarest

Scala macros to generate RESTful Models

GitHub

MetaRest CircleCI Download

Use Scala macros to generate your RESTy models

Let's say you have the following User model in your business layer:

case class User(id: Int, name: String, email: String, registeredOn: DateTime)

But, now you want to create well-formed models to describe the requests/responses of your HTTP REST APIs:

// Response to GET /users/$id (Retrieve an existing user)
case class UserGet(id: Int, name: String, email: String)

// Request body of POST /users (Create a new user)
case class UserPost(name: String, email: String)

//Request body of PATCH /users/$id (Edit name of an existing user)
case class UserPatch(name: Option[String])

That is a lot of boilerplate! Keeping all these request models in sync with your business model and/or adding/removing fields quickly becomes tedious for more complicated models. With MetaRest, all you need to do is:

import com.github.pathikrit.metarest._

@Resource case class User(
  @get               id            : Int,
  @get @post @patch  name          : String,
  @get @post         email         : String,
                     registeredOn  : DateTime
)

The above annotated code would generate code essentially looking like this:

object User {
  case class Get(id: Int, name: String, email: String)
  case class Post(name: String, email: String)
  case class Patch(name: Option[String])        // Note: all fields in a PATCH are optional
}

Now, you can have a well defined CRUD interface for your API:

trait UserRepo {
  def getAll: List[User.Get]
  def get(id: Int): User.Get
  def create(request: User.Post): User.Get
  def replace(id: Int, request: User.Put): User.Get
  def update(id: Int, request: User.Patch): User.Get
  def delete(id: Int): User.Get
}

sbt

In your build.sbt, add the following entries:

resolvers += Resolver.bintrayRepo("pathikrit", "maven")

libraryDependencies += "com.github.pathikrit" %% "metarest" % "2.0.0"

addCompilerPlugin("org.scalameta" % "paradise" % "3.0.0-M8" cross CrossVersion.full)

Although this library currently only supports Scala 2.11+, older versions of this library that used to support Scala 2.10.x are available here.