Ruby: A small summary of what return, break and next means for blocks
Summary
- Use
return
to return from a method.return
accepts a value that will be the return value of the method call. - Use
break
to quit from a block and from the method that yielded to the block.break
accepts a value that supplies the result of the expression it is “breaking” out of. - Use
next
to skip the rest of the current iteration.next
accepts an argument that will be the result of that block iteration.
The following method will serve as an example in the details below:
def example
puts yield
puts ...
whenever: Installing cron jobs only for a given Rails environment or Capistrano stage
We use the whenever gem to automatically update the crontab of the servers we deploy to. By default, whenever will update all servers with a matching role (we use the :cron
role ).
This card describes how to install some tasks only for a given Rails environment or for a given Capistrano stage ("deployment target").
Installing jobs only for a given Rails environment
-----------------------------------...
Middleman configuration for Rails Developers
Middleman is a static page generator that brings many of the goodies that Rails developers are used to.
Out of the box, Middleman brings Haml, Sass, helpers etc. However, it can be configured to do even better. This card is a list of improvement hints for a Rails developer.
Gemfile
Remove tzinfo-data
and wdm
unless you're on Windows. Add these gems:
gem 'middleman-livereload'
gem 'middleman-sprockets' # Asset pipeline!
gem 'bootstrap-sass' # If you want to use Bootstrap
gem 'byebug'
gem 'capistrano'
gem 'capistrano-mid...
RestClient / Net::HTTP: How to communicate with self-signed or misconfigured HTTPS endpoints
Occasionally, you have to talk to APIs via HTTPS that use a custom certificate or a misconfigured certificate chain (like missing an intermediate certificate).
Using RestClient will then raise RestClient::SSLCertificateNotVerified
errors, or when using plain Net::HTTP:
OpenSSL::SSL::SSLError: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed
Here is how to fix that in your application.
Important: Do not disable certificate checks for production. The interwebs are full of people say...
Using Low-Level Prompts for High-Accuracy AI Coding
The key to unlocking the full potential of LLMs in coding lies in crafting precise prompts. The main challenge is learning how to structure prompts effectively to guide the model toward accurate results. Further evidence supporting this is the fact that Aider already writes ~70% of its own code (as of 02/2025). However, when starting out, your results may fall short of efficiently generating large portions of your code with the...
Lightning Talk: Coverage based Test Case Prioritization in Ruby on Rails
For my computer science bachelor's thesis I programmed and evaluated a CLI Test Case Prioritization (TCP) tool for makandra. It has been written as a Ruby Gem and was tested and evaluated against one Ruby on Rails project. This card will summarize and present the research results, the evaluation and the programmed CLI tool.
The code has been published for educational purposes on GitHub. The german bachelor's thesis has also been included for download at the end.
...
Faking and testing the network with WebMock
An alternative to this technique is using VCR. VCR allows you to record and replay real HTTP responses, saving you the effort to stub out request/response cycles in close details. If your tests do require close inspection of requests and responses, Webmock is still the way.
WebMock is an alternative to FakeWeb when testing code that uses the network. You sh...
Too many parallel test processes may amplify flaky tests
By default parallel_tests will spawn as many test processes as you have CPUs. If you have issues with flaky tests, reducing the number of parallel processes may help.
Important
Flaky test suites can and should be fixed. This card is only relevant if you need to run a flaky test suite that you cannot fix for some reason. If you have no issues...
Using CSS transitions
CSS transitions are a simple animation framework that is built right into browsers. No need for Javascript here. They're supported by all browsers.
Basic usage
Transitions are used to animate the path between to property values. For example, to let the text color fade from red to green on hover, the following SASS is used (shorthand syntax):
.element
color: red
transition: color .1s
&:hover
color: green
This tells the browser "whenever the color
of an .element
changes...
Migrating from Elasticsearch to Opensearch: searchkick instructions (without downtime!)
General
A general overview about why and how we migrate can be found under Migrating from Elasticsearch to Opensearch
This card deals with specifics concerning the use of searchkick.
Step 1: Make Opensearch available for Searchkick
In your Gemfile
# Search
gem 'searchkick' # needs to be > 5, to use Opensearch 2
gem 'elasticsearch'
gem 'opensearch-ruby'
in config/initializers/searchkick.rb
(or wherever you have configured your Searchkick settings) add:
SEARCHKICK_CLIENT_T...
How to use pessimistic row locks with ActiveRecord
When requests arrive at the application servers simultaneously, weird things can happen. Sometimes, this can also happen if a user double-clicks on a button, for example.
This often leads to problems, as two object instances are modified in parallel maybe by different code and one of the requests writes the results to the database.
In case you want to make sure that only one of the requests "wins", i.e. one of the requests is fully executed and completed while the other one at least has to wait for the first request to be completed, you ha...
Vortrag: Content Security Policy: Eine Einführung
Grundidee
CSP hat zum Ziel einen Browser-seitigen Mechanismus zu schaffen um einige Angriffe auf Webseiten zu verhindern, hauptsächlich XSS-Angriffe.
Einschub: Was ist XSS?
XSS = Cross Site Scripting. Passiert wenn ein User ungefiltertes HTML in die Webseite einfügen kann.
<div class="comment">
Danke für den interessanten Beitrag! <script>alert('you have been hacked')</script>
</div>
Rails löst das Problem weitgehend, aber
- Programmierfehler weiter möglich
- manchmal Sicherheitslücken in Gems oder Rails
Lösungsid...
Lazy-loading images
Note
This card does not reflect the current state of lazy loading technologies. The native lazy attribute could be used, which is supported by all major browsers since 2022.
Since images are magnitudes larger in file size than text (HTML, CSS, Javascript) is, loading the images of a large web page takes a significant amount of the total load time. When your internet connection is good, this is usually not an issue. However, users with limited bandwidth (i.e. on mobile) need to mine their data budget...
Test-Driven Development with integration and unit tests: a pragmatic approach
Test-Driven Development (TDD) in its most dogmatic form (red-green-refactor in micro-iterations) can be tedious. It does not have to be this way! This guide shows a pragmatic approach with integration and unit tests, that works in practice and improves on productivity.
Advantages
- No added effort: tests need to be written anyway.
- Test heads serve as todo lists. You'll always know what is finished and what is left to do.
- Big tasks are broken down into smaller tasks that can be processed one by one.
- You will not forget a test.
- You...
How to query GraphQL APIs with Ruby
While most Rails Apps are tied to at least one external REST API, machine-to-machine communication via GraphQL is less commonly seen. In this card, I'd like to give a quick intro on how to query a given GraphQL API - without adding any additional library to your existing app.
Core aspects of GraphQL
Interacting with GraphQL feels a bit like querying a local database. You are submitting queries to fetch data in a given structure (like SELECT in SQL) or mutations to alter the database (similar to POST/PUT/DELETE in REST). You can ...
Async control flow in JavaScript: Promises, Microtasks, async/await
Slides for Henning's talk on Sep 21st 2017.
Understanding sync vs. async control flow
Talking to synchronous (or "blocking") API
print('script start')
html = get('/foo')
print(html)
print('script end')
Script outputs 'script start'
, (long delay), '<html>...</html>'
, 'script end'
.
Talking to asynchronous (or "evented") API
print('script start')
get('foo', done: function(html) {
print(html)
})
print('script end')
Script outputs 'script start'
, 'script end'
, (long ...
Gatekeeping: Guide for gatekeeper
If you're responsible for gatekeeping in a projects, here is a guide, what to do.
In order to reduce the number of rejects we get from clients, we want to review all code written before it goes to the staging server.
Note: This process is tailored to our specific needs and tools at makandra. While it will certainly not apply to all (especially larger teams), we think it is a helpful starting point.
First, read the [Gatekeeping for developers](https://makandracards.com/makandra/6579-gatekeeping-guide-for...
Shell script to magically configure display setup
Here is a bash script that I use to auto-configure displays on Ubuntu 24.04 with Xorg.
Background
- Ubuntu always sets the primary display to the 1st (i.e. internal) display whenever I connect to a new Dock/Hub.
- I want my primary display to be the large display.
- My notebook is always placed left of external displays, so the 2nd display will be the center (or only) external display and should be primary.
- I also want all my displays to be placed horizontally, but bottom-aligned (the default would be aligned at their top edges)....
Inspecting a live Ruby process
How to get a backtrace from a running Ruby process:
Ruby 2.6
# First, find out the PID of your Ruby process (e.g. passenger-status)
$ sudo gdb -p PID
(gdb) call rb_eval_string("$stderr.reopen('/tmp/ruby-debug.' + Process.pid.to_s); $stderr.sync = true") # redirects stderr
(gdb) call rb_backtrace() # prints current backtrace to /tmp/ruby-debug.xxx
Stop the process afterwards, since stderr is now borked.
It is possible you have to call rb_backtrace()
multiple times to get the full stacktrace.
Previous method on Ruby 2....
What we know about PDFKit
What PDFKit is
- PDFKit converts a web page to a PDF document. It uses a Webkit engine under the hood.
- For you as a web developer this means you can keep using the technology you are familar with and don't need to learn LaTeX. All you need is a pretty print-stylesheet.
How to use it from your Rails application
- You can have PDFKit render a website by simply calling
PDFKit.new('http://google.com').to_file('google.pdf')
. You can then send the...
routing-filter is broken with Rails 7.1
If you are using the routing-filter gem in your Rails 7.1 app for managing URL segments for locales or suffixes, you will notice that the filters do no longer apply, routes are broken and the necessary parameters are no longer extracted. That is because routing-filter patches Rails' find_routes
-method to get the current path and apply its defined filters on it. These filters then modify the params that are handed over to your controller action. This way you receive a locale
parameter from a ...
Enabling YJIT
YJIT is Ruby's default just-in-time compiler. It is considered production-ready since Ruby 3.2 (source).
To activate YJIT you need two steps:
- Your
ruby
binary needs to be compiled with YJIT support. - You need to enable YJIT.
Getting a Ruby with YJIT support
We usually install Ruby with tools like rbenv
or asdf
. This compiles the ruby
binary from the source code. Support for YJIT
will be automatically added during this compilation...
How to: Ensure proper iconfont rendering with Webpack
Background
After switching a project from Sprockets to Webpack, I started observing a bug that was hard to debug: Our custom icon font could sometimes not be displayed until a full page reload.
Digging deeper the only difference before and after the page load was the encoding interpretation of the iconfont stylesheet:
Correct representation (UTF-8):
.icon:before {
content: ""
}
Broken representation (other charset):
`...
Rails: Testing exceptions with the rescue_responses setting
In Rails 7.2 the new default for config.action_dispatch.show_exceptions
is rescuable
.
-
:rescuable
: It will show a Rails error page in the response only for rescuable exceptions as
defined byActionDispatch::ExceptionWrapper.rescue_responses
. In the
event of an unexpected internal server error, the exception that caused
the error will still be raised within the test so as to provide a useful
stack trace and a good debugging experience. -
:all
: It wi...