OCaml, REborn: fullstack applications with ReasonML

OCaml is a systems language that’s been around for more than 20 years. Reason is a new syntax and toolchain that aims to make OCaml more accessible to everyone.

This talk aims to present Reason / OCaml as a viable alternative to building modern, fullstack, data-driven web applications that share the types of their business objects between the backend and the frontend (much like Clojure programmers are used to with CLJC).

I will also demonstrate how GraphQL, a data-driven query language for APIs, plays nicely with OCaml’s type system to achieve fully type-checked queries across the board, for instance disallowing clients to compile if they’re requesting a piece of data that the backend cannot provide.

From Small FP Conf 2018: https://clojutre.org/2018/#anmonteiro

Transcript

1. OCaml, REborn Fullstack Applications with ReasonML Small FP Conf 2018 @anmonteiro90
2. youtube.com/watch?v=jH1oJiLV7_0
3. Hello! ! anmonteiro.com
5. Back in 2016...
7. Enter Reason — Syntax & toolchain for OCaml — (still OCaml) — github.com/facebook/reason — Goals: — newcomer friendly — extend OCaml's reach
9. What do I like about Clojure? — Easily build fullstack apps that share code — .cljc helps so much here — EDN, Transit roundtripping — the Datomic experience (!)
10. What does this integrated development experience look like in OCaml?
11. OCaml feature rundown ! — Pragmatic, strongly typed systems language — 30+ years of research & development — "80%" coverage / correctness — Multi-purpose, multi-target — Really Fast
12. Several challenges — Types are awesome as long as I don't communicate with the external world — i.e. what happens at the boundary? — Type definitions that span across the stack — How do I share them? — How do I serialize them across the network?
13. Let's take a detour... graphql.org
14. The GraphQL type system GraphQL Type System
15. ! + GraphQL — reconciles GraphQL and OCaml type systems — successful compilation => spec compliant schema
16. Example / Demo
17. Example / Demo $ tree src src !"" client <--- Client specific code (uses Shared) # !"" App.re <--- Queries server GraphQL Schema # $"" Editor.re !"" server <--- Server specific code (uses Shared) # !"" main.re # !"" schema.re <--- GraphQL Schema # $"" server.re $"" shared $"" Shared.re <--- Where shared types live
18. Defining / Using Data type todo = { title: string, completed: bool }; — Server: uses todo type to build GraphQL Schema — Client: uses todo type to model UI — But network communication is untyped...
19. Serializing data — OCaml-GraphQL-Server serializes to JSON — On the client, @bsRecord directive parses into a type in current scope module TodosQuery = [%graphql {| query getTodos { todos @bsRecord { title completed } } |}];
20. ! + GraphQL = " ? — What if we try to query a field that doesn't exist on the server? todos { title completed doesnt_exist }
21. ! + GraphQL = "
22. Parting Thoughts Clojure OCaml / Reason .cljc Compile to JS or Native, shared modules Immutability ✅ EDN / Transit roundtripping GraphQL auto-serialization / custom scalars Datomic Experience ¯\_(ϑ)_/¯
23. Parting Thoughts — GraphQL not really required 1 — What works for me might not work for you — Programs are a living organism [1]: github.com/mjambon/atd
24. Thanks! ! — reason-graphql-fullstack.now.sh — Playground at: reason-graphql-fullstack.now.sh/ graphql — github.com/anmonteiro/reason-graphql-fullstack