melvic-ybanez

Request Validation with Akka-HTTP and Cats

Greg Beech wrote an article on Akka HTTP Entity Validation. This post is on the same topic, except we are going to use typeclass instances, as opposed to subtyping, for form validations.

Sample Problem: User Regsitration

To start with, let us suppose that we are working on some sort of user management service using Scala/Akka. However, here we are only going to focus on the registration part, in which the client is expected to send a user data, in JSON format; and the server needs to validate them, and save the user if the validations succeed, or reject the request with all the errors detected. That said, we should keep in mind that our validations may be used through out the entire codebase, not just in the user registration endpoint.

The rules for our validation are as follows:

gvolpe

Dependency Injection in Functional Programming

There exist several DI frameworks / libraries in the Scala ecosystem. But the more functional code you write the more you'll realize there's no need to use any of them.

A few of the most claimed benefits are the following:

• Dependency Injection.
• Life cycle management.
• Dependency graph rewriting.

knutwalker

package example.statemachine

import scalaz.{State, Scalaz}, Scalaz._

object FSM {
  def apply[I, S](f: PartialFunction[(I, S), S]): FSM[I, S] =
    new FSM((i, s) => f.applyOrElse((i, s), (_: (I, S)) => s))

  private def states[S, O](xs: List[State[S, O]]): State[S, List[O]] =
    xs.sequence[({type λ[α]=State[S, α]})#λ, O]

owainlewis

*.class
*.log

# sbt specific
.cache/
.history/
.lib/
dist/*
target/
lib_managed/

amitchhajer

git ls-files -z | xargs -0n1 git blame -w | perl -n -e '/^.*\((.*?)\s*[\d]{4}/; print $1,"\n"' | sort -f | uniq -c | sort -n