There are two distinct ways of commenting Haml markup: HTML and Ruby.

HTML comments

This will create an HTML comment that will be sent to the client (aka browser):

/= link_to 'Example', 'www.example.com' # => <!-- = link_to 'Example', 'www.example.com' -->

Only use this variant if you need the comment to appear in the HTML.

Ruby comments

This will comment code so it will not be sent to the client:

-# = link_to 'foo'

99% of the time you'll be adding notes for other developers, or disabling code sections that should…

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…

To avoid multiple versions of a package, you can manually maintain a resolutions section in your package.json. We recommend you to do this for packages like jQuery. Otherwise the jQuery library attached to window might not include the functions of your packages that depend on jQuery.

Note: This is only an issue in case you want to use a package functionality from window e.g. $(...).datepicker() from your dev console or any other javascript within the application.

Background

By default yarn will create a folder node_modules …

Many mail clients do not support external style sheets. Some even require all styling inline, which means you'll have to do your styling inline. For Rails applications, you can use Roadie or premailer, which lets you keep your well-structured CSS files and do the inlining for you.

See Designing HTML email

Since Roadie is now in passive maintenance mode, we go with premailer:

Include premailer in your Gemfile:

```
gem 'premailer-ra…

When doing some meta-programming magic and you want to do something for all attributes of a class, you may need to access connection or some of its methods (e.g. columns) during class definition.

While everything will be fine while you are working on a project that is in active development, the application will fail to boot when the database is missing or has no tables. This means that Raketasks like db:create or db:migrate fail on a freshly cloned project.

The reason is your environment.rb which is loaded for Raketasks and calls…

This is a short overview of things that are required to upgrade a project from the Asset Pipeline to Webpacker. Expect this upgrade to take a few days even the diff is quite small afterwards.

Preparations

1. Find all libraries that are bundled with the asset pipeline. You can check the application.js and the application.css for require and import statements. The source of a library is most often a gem or a vendor directory.
2. Find an working example for each library in the application and write it down.
3. Find out the ver…

In Rails, we usually have a mailer setup like this:

class MyMailer < ActionMailer::Base

  def newsletter
    mail to: 'receiver@host.tld',
      from: 'sender@host.tld',
      subject: 'My mail'
  end

end

If you want to preview your mail in the browser, you can use the Action Mailer Preview. To inspect the mail directly in your email client, just create an .eml file and open it with your client:

```ruby
mail = MyMailer.newsletter
Fil…

We generally use multiple application servers (at least two) and you have to search on all of them if you don't know which one handled the request you are looking for.

Rails application logs usually live in /var/www/<project-environment-name>/shared/log.
Web server logs usually live in /var/www/<project-environment-name>/log.

Searching through single logs with grep / zgrep

You can use grep in this directory to only search the latest logs or zgrep to also search older (already zipped) logs. zgrep is used just like grep a…

While deploying an Ruby update to an old application these days, we encountered the following misleading error:

*** [err :: some-host.makandra.de] You are trying to install in deployment mode after changing
*** [err :: some-host.makandra.de] your Gemfile. Run `bundle install` elsewhere and add the
*** [err :: some-host.makandra.de] updated Gemfile.lock to version control.
*** [err :: some-host.makandra.de] 
*** [err :: some-host.makandra.de] You have deleted from the Gemfile:
*** [err :: some-host.makandra.de] *

We found out a newe…

All our projects have enum-like requirements like this:

• An attribute value must be included in a given set of values.
• The list of allowed values must be retrievable in order to render <select> boxes.
• Each value has a humanized label.
• Sometimes there is a default value.

Most of the time, this requirement is also needed:

• The list of assignable values depends on the user who is currently signed in.

In our past projects there are many different solutions for these related requirements, e.g. ChoiceTrait, methods like `available_…

Starting with Ruby 1.9, most #each methods can be called without a block, and will return an enumerator. This is what allows you to do things like

['foo', 'bar', 'baz'].each.with_index.collect { |name, index| name * index }
# -> ["", "bar", "bazbaz"]

If you write your own each method, it is useful to follow the same practice, i.e. write a method that

• calls a given block for all entries
• returns an enumerator, if no block is given

How to write a canonical each method

To write a metho…

Trick: Do not use convert but mogrify:

mogrify -resize 50% *

This overwrites the original image file.

In contrast, convert writes to a different image file. Here is an example if you need this:

cd /path/to/image/directory
for i in `ls -1 *jpg`; do convert -resize 50% $i "thumb_$i"; done