TL;DR Under certain circumstances, dynamically defined symbols may break keyword arguments in Ruby 2.2. This was fixed in Ruby 2.2.3 and 2.3.

Specifically, when …

• there is a method with several keyword arguments and a double-splat argument (e.g. def m(foo: 'bar, option: 'will be lost', **further_options))
• there is a dynamically created Symbol (e.g. 'culprit'.to_sym) that is created before the method is parsed
• the method gets called with both the option and a culprit keyword argument

… then the `optio...

When using send_file (for example for attachments of any kind), make sure your application knows the correct mime types so that all browsers can handle the files. It is much more convenient for users if they can decide to open a file directly instead of having to save it first.

For Rails >= 3.2

Simply put your mime types in config/initializers/mime_types.rb. send_file will take care of everything else.

For Rails < 3.2

Put your mime types in config/initializers/mime_types.rb. Additionally, tell send_file to use them (for ex...

Bad

# Given the following models

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

class Album < ActiveRecord::Base
  has_many :album_images
  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,
   ...

When ending a Selenium test Capybara resets the browser state by closing the tab, clearing cookies, localStorage, etc.

It may be a good idea to wait for all in-flight AJAX requests to finish before ending a scenario:

• You may have client-side JavaScript that freaks out when the tab closure kills their pending requests. If that JavaScript opens an error alert or spams errors to the console, your test may fail after the last step.
• With unlucky timing the server may receive an AJAX request as the browser tab closes, causing a connection ...

You know that ActiveRecord caches associations so they are not loaded twice for the same object. You also know that you can reload an association to make Rails load its data from the database again.

user.posts.reload
# discards cache and reloads and returns user.posts right away
# => [...]

If you want to discard the cache but not query the database (only the next time the association is accessed), you can use reset:

user.posts.reset
# discards cache, but does not load anything yet
user.posts
# SQL query happens to ...

Instead of this:

Image.order('images.created_at DESC')

You can write this:

Image.order(created_at: :desc)

Not only do you not have to write SQL, you also get qualified column names (created_at becomes images.created_at) for free.

Multiple order criteria

To add secondary order criteria, use a hash with multiple keys and :asc / :desc values:

Image.order(title: :asc, created_at: :desc)

It's generally not trivial to change a datetime's seconds, minutes, etc in SQL. Here is how it works when speaking PostgreSQL.

Consider you have a timestamp column whose seconds you want to zero:

SELECT born_at FROM users;
       born_at
---------------------
 2015-05-01 13:37:42

You can the TO_CHAR function to convert date or time values into a string, and do your changes there:

SELECT TO_CHAR(born_at, 'YYYY-MM-DD HH24:MI:00') FROM users;
       to_char
---------------------
 2015-05-01 13:37:00

...

Web applications can be used by multiple users at the same time. A typical application server like Passenger has multiple worker processes for a single app. In a distributed deployment setup like we use at makandra you will even have multiple application servers, each with their own worker pool.

This means that your code needs to deal with concurrent data access. The two main tools we use to cope with concurrency are database transactions and distributed locks. These two are not interchangeable. You ca...

You can hook into Slack when using Capistrano for deployment. The slackistrano gem does most of the heavy lifting for you. Its default messages are unobtrusive and can be adjusted easily.

When deploying, it posts to a Slack channel like this:

How to integrate

Integrating Slackistrano with Capistrano 3 is fairly simple.

1. In your Slack, open menu → A...

See this Railscast.

Basically you can simply write views like index.xlsx.erb:

<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
  xmlns:o="urn:schemas-microsoft-com:office:office"
  xmlns:x="urn:schemas-microsoft-com:office:excel"
  xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
  xmlns:html="http://www.w3.org/TR/REC-html40">
  <Worksheet ss:Name="Sheet1">
    <Table>
      <Row>
        <Cell><Data ss:Type="String">ID</Data></Ce...

Write a // and indent every subsequent line by two spaces.

This is great for documenting BEM blocks!

//
  An action button
  ================
  
  Basic usage
  -----------
  
      <a href="/path" class="action">New booking</a>
      <button class="action">Save</a>
      <input type="submit" class="action">Save</a>
  
  Colors
  -------
  
      <a href="/path" class="action is-red">Primary</a>
      <a href="/path" class="action is-grey">Secondary</a>
  
  Small inline buttons
  --------------------
  
      <p>
        Recor...

Here you are:

SELECT table_name, table_rows FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'your_database' order by table_rows;

Good article about window functions. Also note how they use a postgres feature called common table expressions.

This guide shows how to create an AngularJS application that consumes more and more memory until, eventually, the browser process crashes on your users.

Although this guide has been written for Angular 1 originally, most of the advice is relevant for all client-side JavaScript code.

How to observe memory consumption

To inspect the amount of memory consumed by your Javascripts in Chrome:

• Open an incognito window
• Open the page you want to inspect
• Press Shift + ESC to see a list of Chrome processes...

The linked article explains how to get a database-wide lock without creating table rows:

This article explains how I replaced file-based methods to ensure only one running instance of a program with MySQL’s GET_LOCK function. The result is mutual exclusivity that works in a distributed environment, and it’s dead simple to implement.

Ruby implementation

An implementation as a Rubygem seems to be [with_advisory_lock](https:...

Postgres 9.4 introduces a new column type: jsonb. json and jsonb columns store data differently, so just compare the two when you want to store JSON data and choose the one that matches your use case best.

Rails 4.2 includes support for jsonb columns, too. The article outlines different ways on how to interact with the serialized object.

When you are using the #selector_for helper in Cucumber steps, as e.g. Spreewald does, the following snippet will save you typing. It recognizes a prose BEM-style selector and maps it to the corresponding BEM class.

For a variation on this idea, see An auto-mapper for ARIA labels and BEM classes in Cucumber selectors.

Examples

"the main menu" -> '.main-menu'
"the item box's header" -> '.item-box--header'

Here are some examples of steps (using Spreewald, too):

T...

When running migrations with rake db:migrate, there's the STEP and VERSION parameters that you can pass to nearly all commands.

# Migrate
rake db:migrate
rake db:migrate STEP=2
rake db:migrate VERSION=20080906120000

# Redo
rake db:migrate:redo
rake db:migrate:redo STEP=2
rake db:migrate:redo VERSION=20080906120000

# Rollback (starting from latest migration)
rake db:rollback
rake db:rollback STEP=2

# Run the `down` migration path of a certain migration file
rake db:migrate:down VERSION=20080906120000

tldr; Use git diff -M or git diff --find-renames when you've moved a few files around.

Usage

$ git diff --help
  Options:
    -M[<n>], --find-renames[=<n>]
      Detect renames. If n is specified, it is a threshold on the similarity index
       (i.e. amount of addition/deletions compared to the file’s size). For example,
       -M90% means Git should consider a delete/add pair to be a rename if more than
       90% of the file hasn’t changed. Without a % sign, the number is to be read as
       a fraction, with a decimal point...

greckout query

This will list all branches matching your query as input options for git checkout

  greckout ar
  
  1) ar/cache-api-keys-1098
  2) ar/add-categories-object-to-tv-show-1382
  3) ...

If you want to load an SQL dump from an ActiveRecord migration, you might find this to be harder than you thought. While you can call ActiveRecord::Base.connection.execute(sql) to execute arbitrary SQL commands, the MySQL connection is configured to only accept a single statement per query. If you try to feed it multiple statements, it will die with You have an error in your SQL syntax.

You can work around this by opening a second MySQL connection that does accept multiple statements per call.

Below is an example for a migration that l...

Geordi 1.0 features a command line application geordi, that holds most of Geordi's previous commands.

New features

• command help and usage examples right within geordi (geordi help and geordi help <command>)

• quick command access: type just the first few letters of a command, e.g. geordi rs or geordi dev[server]

• command dependencies, e.g. geordi rspec invokes geordi bundle-install (which bundles only if needed)

• no cluttered /usr/bin, but all commands in one handy tool

• template for easily adding new...

Add gem 'database_cleaner' to your Gemfile. Then:

Cucumber & Rails 3+

# features/support/database_cleaner.rb

DatabaseCleaner.clean_with(:deletion) # clean once, now
DatabaseCleaner.strategy = :transaction
Cucumber::Rails::Database.javascript_strategy = :deletion

Cucumber & Rails 2

The latest available cucumber-rails for Rails 2 automatically uses database_cleaner when cucumber/rails/active_record is required -- but only if transactional fixtures are off. To have database_cleaner work correctly:

1. Add the at...

Some insight into how browser rendering engines work. The article shows how the way you manipulate styles (and the DOM) can affect rendering performance by forcing the browser to re-paint large portions of the screens, or re-calculate the dimensions of a large subtree of DOM nodes.