Sending newsletters via rapidmail with SMTP and one-click unsubscribe
If you need to implement newsletter sending, rapidmail is a solid option.
Support is very fast, friendly and helpful, and the initial setup is simple. Since rapidmail works via SMTP, you can simply ask the Ops team to configure SMTP credentials for your application.
You also do not need to use rapidmail’s built-in newsletter feature. Instead, you can send emails as transactional mails, which allows you to keep the entire newsletter logic inside your application.
One thing to keep an ey...
Ruby: How to collect a Hash from an Array
There are many different methods that allow mapping an Array to a Hash in Ruby.
Array#to_h with a block (Ruby 2.6+)
You can call an array with a block that is called with each element. The block must return a [key, value] tuple.
This is useful if both the hash key and value can be derived from each array element:
users = User.all
user_names_by_id = users.to_h { |user| [user.id, user.name] }
{
1 => "Alice",
2 => "Bob"
}
Array#to_h on an array of key/value tuples (Ruby 2.1+)
Converts an Array ...
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...
Controlling how your website appears on social media feeds
When a user shares your content, a snippet with title, image, link and description appears in her timeline. By default social networks will use the window title, the first image, the current URL and some random text snippet for this purpose. This is often not what you want.
Luckily Facebook, Twitter, etc. lets you control how your content appears in the activity streams. They even have agreed on a common format to do this: OpenGraph <meta> tags that go into your HTML's <head>:
<meta property="og:url" content="http://start.m...
Fixing authentication in legacy applications
Authentication is hard: there are many edge cases, and most users (including yourself) usually only go the "happy path" once and never see the edge cases. If you have rolled your own authentication, or been using older authentication solutions, or resorted to HTTP Basic Authentication, this card will tell you what to do to make your application safe.
Any application that stores sensitive data in the browser
That is: cookies, e.g. by offering a login.
- Ask the admins to [turn on SSL](https://makandracards.com/makandra/1416-integrate-s...
How to: Benchmark an Active Record query with a Ruby script
Recently I needed to benchmark an Active Record query for performance measurements. I wrote a small script that runs each query to benchmark 100 times and calculates the 95th percentile.
Note: The script requires sudo permissions to drop RAM cache of PostgreSQL. Due to the number of iterations it was impractical to enter my user password that often. And I temporary edited my /etc/sudoers to not ask for the sudo password with johndoe ALL=(ALL) NOPASSWD: ALL.
# Run this script with e.g. `rails ru...
WYSIWYG with Action Text
Rails 6 includes a WYSIWYG editor, Action Text. It works out of the box quite well, but chances are that you want to add some custom functionality. This card contains some tips how to achieve this.
Setup
Basically, follow the guide in the Rails documentation. The automated script may not work with the way webpacker is configured in your project, but it should be easy to fix.
If you don't want the default c...
PSA: Be super careful with complex `eager_load` or `includes` queries
TLDR
Using
.includesor.eager_loadwith 1-n associations is dangerous. Always use.preloadinstead.
Consider the following ActiveRecord query:
BlogPost.eager_load(
:comments
:attachments,
).to_a
(Let's assume we only have a couple of blog posts; if you use pagination the queries will be more complicated, but the point still stands.
Looks harmless enough? It is not.
The problem
ActiveRecord will rewrite this into a query using LEFT JOINs which looks something like this:
SELECT "blog_posts...
How to enable pretty IRB inspection for your Ruby class
When Ruby objects are inspected in any modern IRB, some objects (like ActiveRecord instances) are rendered with neat colors and line breaks.
You will not get that for custom classes by default -- which can be annoying if your inspection contains lots of meaningful information.
Here is what you need to do if you want your objects to be inspected nicely.
Implement a pretty_print method
As an example, consider the following class.
class MyClass
# ...
def inspect
"#<#{self.class} attr1: #{attr1.inspect}, attr2: #{attr2...
How the Date Header Affects Cookie Expiration and Caching
tl;dr
When a cookie includes an
Expiresattribute or an HTTP response includes caching headers likeExpiresorCache-Control, their validity depends on the server'sDateheader if present. Otherwise, the browser uses its local time. This can lead to issues in tests with mocked time or inconsistent cache behavior.
Cookie Expires depends on the Date header or browser time
When a cookie includes an Expires attribute, the browser evaluates the expiration date relative to a reference time:
- If the HTTP response ...
Regular tasks for long-running projects
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, Unpoly) should always be reasonably up to da...
has_one association may silently drop associated record when it is invalid
This is quite an edge case, and appears like a bug in Rails (4.2.6) to me.
Update: This is now documented on Edgeguides Ruby on Rails:
If you set the :validate option to true, then associated objects will be validated whenever you save this object. By default, this is false: associated objects will not be validated when this object is saved.
Setup
# post.rb
class Post < ActiveRecord::Base
has_one :attachment
end
# attachm...
Center a float horizontally
This card shows you how to center a float horizontally in CSS. Also: find out what techniques are available for your use case and browser requirements in the card linked below.
Note: We have card with all CSS centering options. You probably want to head over there and get an overview over what techniques are available for your use case and browser requirements.
If you cannot use display: inline-block, centering a float ...
GoodJob: Ensure you get notified about background exceptions
GoodJob and ActiveJob rescue exceptions internally, preventing exception_notification from triggering. This can cause silent job failures.To get notified, subscribe to ActiveJob events and configure GoodJob's on_thread_error hook. This lets you manually call your exception notifier for every retry, discard, or internal GoodJob error.
# config/initializers/good_job.rb
# Manually notify on job failures, as they are handled internally by ActiveJob/GoodJob.
ActiveSupport::Noti...
Switching the package manager from yarn to npm
We recently migrated a Rails application from yarn to npm. We decided to go this step instead of upgrading to > Yarn 2.0 to reduce the number of dependencies in our project.
Migration
- Remove the
yarn.lockfile - Remove the
node_modulesfolder - Run
npm install - Replace all occurrences of
yarnwithnpmin your project
Notes
- With
npmvendored packages with dependencies create their ownnode_modulesfolder within the vendor path. We...
Ruby: How to use prepend for cleaner monkey patches
Let's say you have a gem which has the following module:
module SuperClient
def self.foo
'Foo'
end
def bar
'Bar'
end
end
For reasons you need to override foo and bar.
Keep in mind: Your code quality is getting worse with with each prepend (other developers are not happy to find many library extensions). Try to avoid it if possible.
- Add a
lib/ext/super_client.rbto your project (see How to organize monkey patches in Ruby on Rails projects) - Add the extension, which ov...
Capybara: Preventing server errors from failing your test
When your Rails application server raises error, Capybara will fail your test when it clears the session after the last step. The effect is a test that passes all steps, but fails anyway.
Capybara's behavior will help you to detect and fix errors in your application code. However, sometimes your application will explode with an error outside your control. Two examples:
- A JavaScript library references a source map in its build, but forgets to package the source map
- CarrierWave cleans up an upload or cache file after the record was delet...
How to turn images into inline attachments in emails
Not all email clients support external images in all situations, e.g. an image within a link. In some cases, a viable workaround is to turn your images into inline attachments.
Note
Rails provides a simple mechanism to achieve this:
This documentation makes it look like you have to care about these attachments in two places. You have to create the attachment in t...
JSON APIs: Default design for common features
When you build a JSON API you need to come up with a style to represent attributes, pagination, errors or including associated objects. Instead of reinventing the wheel, you may reuse successful API designs.
JSON API
JSON:API specifies common features found in most JSON APIs, like pagination, ordering and nested resources. The spec looks very similar to how one would build an API with Rails and uses similar patterns. Even if you don't plan on supporting the whole spec, it can still make sense to know how th...
Disable PostgreSQL's Write-Ahead Log to speed up tests
The linked article suggests an interesting way to speed up tests of Rails + Postgres apps:
PostgreSQL allows the creation of “unlogged” tables, which do not record data in the PostgreSQL Write-Ahead Log. This can make the tables faster, but significantly increases the risk of data loss if the database crashes. As a result, this should not be used in production environments. If you would like all created tables to be unlogged in the test environment you can add the following to your...
Making minimal updates to DOM trees using morphdom / idiomorph
When you replace parts of the DOM with new HTML, using .innerHTML = newHtml is usually the simplest and fastest option. It comes at the price of your DOM elements losing state, like input values, scroll position, progress in a video player, or even more complex state for custom elements.
One option to avoid this are libraries like morphdom (as used by Phoenix Liveviews) or idiomorph (as used by Rails' Turbo).
It lets you write
morphdo...
How to tell ActiveRecord how to preload associations (either JOINs or separate queries)
Remember why preloading associations "randomly" uses joined tables or multiple queries?
If you don't like the cleverness of this behavior, you can explicitely tell ActiveRecord how to preload associations with either JOINs or separate queries.
This card gives an overview of the different options to preload associations, but
__Whic...
Ensure passing Jasmine specs from your Ruby E2E tests
Jasmine is a great way to unit test your JavaScript components without writing an expensive end-to-end test for every small requirement.
After we integrated Jasmine into a Rails app we often add an E2E test that opens that Jasmine runner and expects all specs to pass. This way we see Jasmine failures in our regular test runs.
RSpec
In a [feature spec](https://web.archive.org/web/20150201092849/http://www.rel...
Disable SimpleCov if you only run a fraction of your tests
Coverage reports are rarely useful if you run only small parts of your test suite.
Just do not load SimpleCov in this case, and you will see less noise in your test output:
if RSpec.configuration.files_to_run.count > 5
require "simplecov"
SimpleCov.start 'rails'
end