Rails migrations allow you to use a change method whose calls are automatically inverted for the down path. However, if you need to some path-specific logic (like SQL UPDATE statements) you can not define up and down methods at the same time.

If you were to define define all 3 of them, Rails would only run change and ignore up and down. However, Rails 4+ features a helper method called reversible:

class MyMigration < ActiveRecord::Migration

  def...

TLDR: A function is hard to use when it sometimes returns a promise and sometimes throws an exception. When writing an async function, prefer to signal failure by returning a rejected promise.

The full story

When your function returns a promise ("async function"), try not throw synchronous exceptions when encountering fatal errors.

So avoid this:

```
function foo(x) {
if (!x) {
throw "No x given"
} else
return new Promise(function…

We figured out, that ActiveJob Inline might lead to autoloading problems in development. The result was an exception when running an import script, which delivers async mails.

A copy of XXX has been removed from the module tree but is still active! (ArgumentError)

Our fix was to use .deliver_now and not .deliver_later (this is not a general fix, but it was okey for us). Below there are some debug hints which helped us to locate the problem:

• We placed a pry debugger in [ActiveSupport#clear](https://github.com/rails/rails/blob…

When projects run for many years, they require special regular maintenance to stay fresh. This kind of maintenance is usually not necessary for small or quick projects, but required to keep long-running projects from getting stale.

You should be able to fit this into a regular development block.

Quarterly

Check which libraries need updating

As time goes by, libraries outdate. Check your software components and decide if any of it needs an update. Your main components (e.g. Ruby, Rails, Angular) should always be reasonably up to dat…

If your Rubymine does not recognize a file type correctly although you have entered the unmistakeable file extension like material_orders_controller.rb, this may help you:

Causing the Problem

Sometimes you create a new file and forget to enter the ending like material_orders_controller
Rubymine handles such files per default as simple txt files.
You delete this file and create a new one with correct ending: material_orders_controller.rb. But still Rubymine treats this file as text file, no highlighting is available.

What happene…

Use protocol independent URLs whenever possible so that the browser will choose the protocol related to the protocol which the page is delivered with.

Example issues

• When your page is delivered via https and you provide a youtube video only via http the most browsers (e.g. Firefox, Chrome) won't display the video.
• When you deliver your youtube video via https://youtu.be/jyElDp98HdI your test which checks that the embeded video is rendered in the view will fail because your test server doesn't use https

Solution

Let your lin…

When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.

Different screen sizes and browsers

Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?

• Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
• Use @media queries to build a responsive design
  • If you do not suppo…

The exception_notification gem supports to provide custom data to e.g. the fail mail within foreground or background jobs.

ExceptionNotifier.notify_exception(_ex_, :data => {:message => "was doing something wrong"})

Still this can be blocked if you have an initializer where you override the default sections and background_sections option. So remember to add the data option to the desired section if required. In case you raise an exception without a data object, the fail…

When you created a project on the Google API Console which is not being used, you may receive an e-mail like the following one.

This is to inform you that we noticed your project(s) has not accessed or used the YouTube Data API Service in the past 60 days.

For reference, your inactive project number is …

While projects do have names, the e-mail will only tell you its (generated) number. But if you use the API Console's search, you won't get any results for project numbers. Also, project numbers are not visible when you click and …

Accessing pseudo elements via JavaScript or jQuery is often painful/impossible. However, accessing their styles is fairly simple.

Using getComputedStyle

First, find the element in question.

let element = document.querySelector('.my-element') // or $('.my-element').get(0) when using jQuery

Next, use JavaScript's getComputedStyle. It takes an optional 2nd argument to filter for pseudo elements.

```javascript
let style = window.getComputedStyle(element, '::before')
let color = style.getPropertyValue('background-color…

Bad

# Given the following models

class Image < ActiveRecord::Base
  has_many :album_image
  has_many :albums, through: :album_images
end

class Album < ActiveRecord::Base
  has_many :album_image
  has_many :images, through: :album_images
end

# Join model
class AlbumImage < ActiveRecord::Base
  belongs_to :album
  belongs_to :image
end

Destroying a record in this setup will only remove the record itself, and leave orphaned join records behind.

```
image = Image.last
image.destroy # removes only the image record,
…