vaz

Rails Asset Pipeline - Overview/Cheatsheet

Notes based on a lecture by vaz at Lighthouse Labs, Vancouver.

Note: this was based on Rails 4, and while most things haven't changed much and this still covers the concepts pretty well, make sure you've got the Rails Guide docs for the version you're actually using and keep in mind some things may have changed.

What is an asset?

vaz

mergesort :: (Ord t) => [t] -> [t]
mergesort [] = []
mergesort [x] = [x]
mergesort xs = (mergesort ls) `merge` (mergesort rs)
    where (ls,rs) = split xs
          split (x:y:zs)  = let (xs,ys) = split zs in (x:xs,y:ys)
          split [x]       = ([x],[])
          split []        = ([],[])
          merge xs []     = xs
          merge [] ys     = ys

vaz

// If the first statement in a file or a function is "use strict"
// then Strict Mode will be activated for that file or function.
//
// You could invoke strict mode for the file by uncommenting this:
// "use strict";

function nonStrictFunction () {
  x = 123; // undeclared!
}

vaz

# ActiveRecordish pattern
def create
  @thing = Thing.create!(thing_params)
  redirect_to @thing
rescue Thing::Invalid #???
  # flash error
  # re-render
end

vaz

// this is coming from a library
function delayedValue(x) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(x), 1000)
  })
}

// module doQuery.js
function doQuery() {
  return delayedValue({

vaz

// Promises example
//

// just a helper, which returns a promise that resolves after
// 500-1000 milliseconds with whatever `args` were passed in
function fakeKnex(...args) {
  return new Promise((resolve, reject) => {
    setTimeout(
      function() { resolve(...args) },
      500 + (Math.floor(Math.random() * 500)))

vaz

var request = require('request');

var url = 'http://www.google.com';

// basic use
request.get(url, function(err, response, body) {
  if (err) {
    console.log("Error:", err);
  } else {
    // response.body == body

vaz

Vagrant fixes for file-watching servers

These snippets show how to enable polling for filesystem changes when using

• nodemon for Node apps (ExpressJS, etc)
• rails server
• webpack-dev-server --watch
• ember server

You can probably look at these examples and Google to find similar solutions for other dev servers.

vaz

Knex seeds: associating records

It's easiest if you're associating records between tables if you do it in one seed file. There are other ways but for now this is probably easiest.

PostgreSQL will generate your id fields for you, so don't put them in your seeds! Instead, take advantage of the returning chainable method from knex. See the below seed file and also http://knexjs.org docs.

vaz

function benchmark(cb) {
  const start_time = 12345;

  const result = cb('some message');
  console.log("the return value of cb was: ", result);

  const end_time = 12456;
  return end_time - start_time
}