Build your web API on the type level.
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Latest commit b5703c6 Dec 3, 2018

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Define type safe APIs and let the Scala compiler do the rest:

Api definition

import typedapi._

val MyApi =
  // GET {body: User} /fetch/user?{name: String}
  api(method = Get[MT.`application/json`, User], 
      path = Root / "fetch" / "user", 
      queries = Queries add Query[String]('name)) :|:
  // POST {body: User} /create/user
  apiWithBody(method = Post[MT.`application/json`, User], 
              body = ReqBody[Json, User], 
              path = Root / "create" / "user")

And for the Servant lovers:

import typedapi.dsl._

val MyApi = 
  // GET {body: User} /fetch/user?{name: String}
  (:= :> "fetch" :> "user" :> Query[String]('name) :> Get[MT.`application/json`, User]) :|:
  // POST {body: User} /create/user
  (:= :> "create" :> "user" :> ReqBody[Json, User] :> Post[MT.`application/json`, User])

Client side

import typedapi.client._

val (fetch, create) = deriveAll(MyApi)

import typedapi.client.http4s._; import cats.effect.IO; import org.http4s.client.blaze.Http1Client

val cm = ClientManager(Http1Client[IO]().unsafeRunSync, "http://my-host", 8080)

fetch("joe").run[IO](cm): IO[User]

Server side

import typedapi.server._

val fetch: String => IO[Result[User]] = name => findUserIO(name).map(success)
val create: User => IO[Result[User]] = user => createUserIO(user).map(success)

val endpoints = deriveAll[IO](MyApi).from(fetch, create)

import typedapi.server.http4s._; import cats.effect.IO; import org.http4s.server.blaze.BlazeBuilder

val sm     = ServerManager(BlazeBuilder[IO], "http://my-host", 8080)
val server = mount(sm, endpoints)


This is all you have to do to define an API with multiple endpoints and to create a working client and server for them.

You can find the above code as a complete project here.


This library is the result of the following questions:

How much can we encode on the type level? Are we able to describe a whole API and generate the call functions from that without using Macros?

It is inspired by Servant and it provides an API layer which is independent of the underlying server/client implementation. Right now Typedapi supports:

If you need something else take a look at this doc.

Get this library

It is available for Scala 2.11, 2.12 and ScalaJS and can be downloaded as Maven artifact:

// dsl
"com.github.pheymann" %% "typedapi-client" % <version>
"com.github.pheymann" %% "typedapi-server" % <version>

// http4s support
"com.github.pheymann" %% "typedapi-http4s-client" % <version>
"com.github.pheymann" %% "typedapi-http4s-server" % <version>

// akka-http support
"com.github.pheymann" %% "typedapi-akka-http-client" % <version>
"com.github.pheymann" %% "typedapi-akka-http-server" % <version>

// Scalaj-Http client support
"com.github.pheymann" %% "typedapi-scalaj-http-client" % <version>

// ScalaJS client support
"com.github.pheymann" %% "typedapi-js-client" % <version>

You can also build it on your machine:

git clone
cd typedapi
sbt "+ publishLocal"


Typedapi also offers an improved experience for Ammonite and ScalaScripts:

import $ivy.`com.github.pheymann::typedapi-ammonite-client:<version>`

import typedapi._
import client._
import amm._

val Readme = api(Get[MT.`text/html`, String], Root / "pheymann" / "typedapi" / "master" / "")
val readme = derive(Readme)

// gives you the raw scalaj-http response
val cm = clientManager("")
val response = get().run[Id].raw(cm)


In case Ammonite cannot resolve com.dwijnand:sbt-compat:1.0.0, follow this solution.


The documentation is located in docs and covers the following topics so far:



Contributions are highly appreciated. If you find a bug or you are missing the support for a specific client/server library consider opening a PR with your solution.