3891 cards
Linked contentRepeats

Geordi hints

Reminder of what you can do with Geordi.

Note: If you alias Geordi to something short like g, running commands gets much faster!
Note: You only need to type the first letters of a command to run it, e.g. geordi dep will run the deploy command.

geordi deploy

Guided deployment, including push, merge, switch branches. Does nothing without confirmation.

geordi capistrano

Run something for all Capistrano environments, e.g. geordi cap deploy

geordi setup -t -d staging

When you just c...


Do not pass an empty array to ActiveRecord.where when using NOT IN

Be careful with the Active Record where method. When you accidentally pass an empty array to the where method using NOT IN, you probably will not get what you expected:

User.where("id NOT IN (?)", [])
=>  SELECT `users`.* FROM `users` WHERE (id NOT IN (NULL))

Even though you might expect this to return all records, this actually results none.

Never use the expression id NOT IN (?) without taking care of this case! See below some workarounds.

Rails < 4

Rails < 4 does not provide a pretty workaround.

ids = []

Linked contentRepeats

How to write a good changelog

We want to keep a changelog for all gems we maintain. There are some good practices for writing a changelog that adds value, please stick to these.

  • Add a notice to the README's contribute section about the changelog
  • For every release update the changelog
  • Note the date format yyyy-mm-tt

What is a changelog?

A changelog is a file which contains a curated, chronologically ordered list of notable changes for each version of a project.

Why keep a changelog?

To make it easier for users and...

Emulating document.currentScript in old browsers

When you need the DOM node of a <script> tag (e.g. to read extra attributes, or to modify the DOM near it), you can usually reference it via document.currentScript.
However, document.currentScript is unsupported in ancient browsers, like Internet Explorer 11 or wkhtmltopdf's Webkit engine.

If you are not running async scripts, you can easily polyfill it:

document.scripts[document.scripts.length - 1]

It works because document.scripts grows with each <script> tag that was evaluated.
That is also the reason why th...

Linked contentAuto-destruct in 27 days

Updated: Controlling how your website appears on social media feeds

  • Added info that Facebook only supports 1.91:1 (will still crop to fit)

Capistrano: Deployment issue undefined method `[]' for nil:NilClass

In newer passenger versions the output of passenger -v has changed. capistrano-passenger tries to parse the version and now causes the error undefined method '[]' for nil:NilClass. To fix this you only need to upgrade the capistrano-passenger gem.

Therefore run bundle update capistrano-passenger.

The version change of passenger from 6.0.7 to 6.0.8 has triggered this problem. This is fixed in capistrano-passenger >= 0.2.1.

Linked contentRepeats

Getting permanent links to files on Github or Gitlab

Please don't simply copy line number links from Github. The URL usually contains a branch name like master which will change over time:


If someone now posts an insertion or deletion to that file into master your link points to the wrong line!

A better way is to press the Y key after clicking on a line number. This will transform the URL to another URL that points to the particular commit:


Copying validation errors from one attribute to another

When using virtual attributes, the attached trait can be useful to automatically copy errors from one attribute to another.

Here is a typical use case where Paperclip creates a virtual attribute :attachment, but there are validations on both :attachment and :attachment_file_name. If the form has a file picker on :attachment, you would like to highlight it with errors from any attribute:

class Note < ActiveRecord::Base
  has_attached_file :attachment
Linked contentRepeats

How to explain SQL statements via ActiveRecord

ActiveRecord offers an explain method similar to using EXPLAIN SQL statements on the database.

However, this approach will explain all queries for the given scope which may include joins or includes.

Output will resemble your database's EXPLAIN style. For example, it looks like this on MySQL:

User.where(id: 1).includes(:articles).explain
EXPLAIN for: SELECT `users`.* FROM `users`  WHERE `users`.`id` = 1
| id | select_type | table | type  | possible_keys |
Linked contentRepeats

The developer console can do more than you think!

You can do so much more than console.log(...)! See the attached link for a great breakdown of what the developer console can give you.

Some of my favorites:

console.log takes many arguments

E.g. console.log("Current string:", string, "Current number:", 12)

Your output can have hyperlinks to Javascript objects

E.g. console.log("Check out the current %o, it's great", location)



Tod: A Gem for handling daytime without a date

Tod is a gem for working with daytimes.

Another additional gem?

Thus SQL has a time datatype for storing time of day in the format hh:mm:ss, neither Ruby nor Rails themselves offer an elegant way to deal with day times.

Time and DateTime both handle daytime values AND calendar date, using them to only store the time of day will end in inconsistent and thus confusing data, e. g. Time.new will initialize with the current Time in your Timezone, DateTime.new initializes at January 1, at an undefined year, without a timezone o...


Git: How to configure git to push only your current branch

You can change which branches will be pushed when saying git push. Our recommendation is to set it to current.

From the git-config documentation:

: ^
Defines the action git push should take if no refspec is given on the command line, no refspec is configured in the remote, and no refspec is implied by any of the options given on the command line. Possible values are:

  • nothing - do not push anything.
  • matching - push all matching branches. All bra...

Deliver Carrierwave attachments to authorized users only


To attach files to your records, you will need a new database column representing the filename of the file. To do this, add a new migration (rails g migration <name>) with the following content:

class AddAttachmentToNotes < ActiveRecord::Migration[6.0]
  def change
    add_column :notes, :attachment, :string

Don't forget to rename the class and change the column details to fit your purpose. Run it.

1) Deliver attachments through Rails


Linked contentRepeats

What does 100% mean in CSS?

The attached article examines what the percent unit (%) is relative to in CSS

The article does a great job of visualizing the dependencies. The TLDR is:

Own property % of
height parent height
width parent width
top parent height
left parent width
margin-top parent width
margin-left parent width
padding-top parent width
padding-left parent width
translate-top own height
Linked contentRepeats

cucumber_factory 1.14 lets you set array fields, has_many associations, numbers without quotes

Setting array columns

When using PostgreSQL array columns, you can set an array attribute to a value with square brackets:

Given there is a movie with the tags ["comedy", "drama" and "action"]

Setting has_many associations

You can set has_many associations by referring to multiple named records in square brackets:

Given there is a movie with the title "Sunshine"
And there is a movie with the title "Limitles...

Why has_many :through associations can return the same record multiple times

An association defined with has_many :through will return the same record multiple times if multiple join models for the same record exist. To prevent this, you need to add ->{ uniq } as second argument to has_many (below Rails 4 it is a simple option: has_many :xyz, :uniq => true).


Say you have an Invoice with multiple Items. Each Item has a Product:

class Invoice < ActiveRecord::Base
  has_many :items
  has_many :products, :through => :items

class Item < ActiveRecord::Base

Using Passenger Standalone for development

For our production servers we use Passenger as a Ruby application server. While it is possible to use Passenger for development as an Apache module, the installation process is not for the faint of heart.

Luckily Passenger also comes as a standalone binary which requires zero configuration.

You can Passenger Standalone as a replacement for Webrick or Thin if you'd like to:

  • Use SSL certificates locally
  • Get performance behavior that is closer to ...

Converting ES6 to ES5 on the command line

I use the TypeScript compiler for this, since its output is more minimal than Babel's.

The following will transpile all src/*.js files into a file build.js:

npm install typescript
npx tsc src/*.js --target ES5 --allowJs --outFile build.js

The output will only transpile ES6 syntax. It will not include any polyfills for missing APIs.

This website uses short-lived cookies to improve usability.
Accept or learn more