dra1n

What is dhall?

• Dhall is a programmable configuration language that you can think of as: JSON + functions + types + imports

Functions

• Built-in
• User defined

let makeUser = \(user : Text) ->
      let home       = "/home/${user}"
 let privateKey = "${home}/.ssh/id_ed25519"

dra1n

const range = (start: number, end: number) =>
  Array.from({ length: end - start + 1 }, (v, k) => k + start);

/* Monad */
const ret = <T>(x: T): T[] => [x];
const bind = <T>(xs: T[], f: (v: T) => T[]): T[] => xs.map(f).flat();
const fail = <T>(_: T): T[] => [];

/* Knight problem */
type KnightPos = [number, number];

dra1n

// user module
const receive = (_user, sender, message) => {
  console.log(`${new Date().toLocaleString()} [${sender}]: ${message}`);
};

// chat room module
const createChatRoom = (users = []) => ({
  users
});

dra1n

class ChatRoom {
  constructor(users = []) {
    this.users = users;
  }

  addUser(user) {
    this.users.push(user);
  }

  sendMessage(user, message) {

dra1n

const execute = (command, ...args) => command(...args);

function PlaceOrderCommand(order, id) {
  return orders => {
    const result = [...orders, { id }];
    console.log(`You have successfully ordered ${order} (${id})`);

    return { success: true, result };
  };
}

dra1n

(ns number-puzzles.imbaru
  (:refer-clojure :exclude [==]) ;; Prevent ns conflict
  (:require [clojure.core.logic :refer :all]))

(def answers (run* [q]
                   (fresh [r1 r2 r3 r4
                           r5 r6 r7 r8
                           r9 r10 r11 r12
                           r13 r14 r15 r16]

dra1n

Teaching New Toys Old Tricks

What's in the toolbox?

• createSlice
• createAction
• createAsyncThunk
• configureStore

What's the slice?

dra1n

Where we left

• UI should be an afterthought
• Write code that allows to sepearate business logic frow UI.
• Write code that allows to inject any hard-to-test, too-verbose, want-this-mocked stuff logic.

Is redux a good tool for impelmenting these ideas?

• It has special place for handling business logic, called middleware.
• Popular middleware have a mechanism for context injection. If you are writing your own custom middleware, then you probably should think about adding this too.

dra1n

UI should be an afterthought

What this logic separation gives?

• Better testability via the fewer levels of indirection. To trigger business processes you call methods or invoke functions, not clicking buttons.
• Better testability via DI in some form. In React code jest.mock is the only "unobtrusive" way to replace dependencies.
• Discoverability. Business logic isn't scattered across a bunch of components.
• Reusability. Sometimes you want to reuse only business logic and not the UI tied to it.
• Readability. It is easier to reason about business logic.

dra1n

What it gives?

• Visual documentation

  • Discoverability (Easier to find existing components. Potentially works for designers too. As a result, we are saving time because we are not doing the same thing again and again)
  • Regression (Breaking design or API changes will be reflected)
  • Describes component API (And edge cases)
  • Hints to intended usage

• Faster design delivery (than having component embedded into the page)

• Early design feedback