When a Rails controller action should handle both HTML and JSON responses, do not use request.xhr? to decide that. Use respond_to.

I've too often seen code like this:

def show
  # ...
  if request.xhr?
    render json: @user.as_json
  else
     # renders default HTML view
  end
end

This is just plain wrong. Web browsers often fetch JSON via XHR, but they (should) also send the correct Accept HTTP header to tell the server the data they expect to receive.

If you say request.xhr? as a means for "…

I recently had fun with replacing a custom video plattform ("mycustomtv") in one of our applications. I learned a lot about naming stuff.

youtube_mycustomtv_chooser is a bad name for a directive.

Why?

• if you add, for example, other video systems like vimeo, the name of the method either lies or will get longer.
• if you replace one system, you will have to change the method and all of its occurrences (and you're very lucky if it is only one poorly named thing in your application)

What would be a better solution?

Abstract fro…

When installing gems, a lot of time is spent building locally installed documentation that you probably never use.

We recommend you disable documentation generation for gem install by default.
Note that Bundler won't install documentation, so this advice applies only when installing gems manually.

If you don't already have it, create a ~/.gemrc file. The gemrc is a Yaml file, so add the following line to add default switches to the gem command.

gem: --no-document

(If you do n…

Enumerable#all? returns true for an empty collection. This totally makes sense but you have to think about it when making assumptions on relations which might be empty.

[].all?(&:will_never_be_called_here) => true

Example with empty collection

class Researcher < ActiveRecord::Base
  has_many :papers
end

class Paper
  validates :topic, inclusion: { in: ['computer_science', 'mathematics', 'economy'] }
end

Easy goal: Delete all researches who write onl…

If you need to test interaction with a remote API, check out the VCR gem as an alternative to Webmock or stubbing hell.

The idea behind VCR is that is performs real HTTP requests and logs the interaction in a .yml file. When you run the test again, requests and responses are stubbed from the log and the test can run offline.

It's a great way to mock network requests to an external service without going through the pain of logg…

ActiveSupport::Dependencies takes care of auto-loading any classes in development. This is usually useful, but when you run into issues with the Rails autoloader, you should take a look at what it's doing.

For me this was useful in an "exciting" case of auto-loading classes inside a thread which caused the application to stop responding.

Rails 4.x

ActiveSupport::Dependencies includes logging support. It is easy to use:

ActiveSupport::Dependencies.logger = Rails.logger

Rails 5+

[Logging support was removed](https://github…

Watch out when saying something like 1.year in Rails. The result is not a Fixnum and can cause unexpected errors when the receiving end expects a Fixnum.

While anything from seconds to months are Fixnums, a year is a Float in Rails – when called on a Fixnum itself:

>> 10.seconds.class
=> Fixnum
>> 2.minutes.class
=> Fixnum
>> 24.hours.class
=> Fixnum
>> 28.days.class
=> Fixnum
>> 9.months.class
=> Fixnum
>> 1.year.class
=> Float # Boom.

While they are [technically correct](http:…

Features

• Generating a project README
• Finally: Support for modelling associations between models in your application model! Example:

# lib/katapult/application_model.rb

model 'Cart' do |cart|
  cart.belongs_to 'User'
end

crud 'User' do |user|
  user.attr :fullname
end

When you have a pending Cucumber step (or feature) that also uses an existing VCR cassette, your pending test may fail at the very end with an error like this:

There are unused HTTP interactions left in the cassette:
  - [get ...] => [200 ...]
  - [get ...] => [200 ...] (VCR::Errors::UnusedHTTPInteractionError)

The error happens because your VCR is configured to complain about cassettes that contain extra requests which your test did not use. This is often a good configuration.
If you do not want to change your whole test suite…

Say you want to move a git repository from one remote (perhaps Github) to another (perhaps Gitlab).

If you have the repo checked out, you still should make sure to mirror all branches of the old remote, not only those you happen to have checked our. Otherwise the target repo will become a copy of your current repo, and not the source repo, potentially missing commits. You can use this:

```
git rename origin old-origin
git remote add origin git fetch old-origin --prune git push --prune origin +refs/remotes/old-origin/*:refs/hea...

When working with times and dates in Rails applications, you need to deal with the following problem:

• In Rails, Time objects have a time zone. You can get the zone name by doing time_object.zone.
• This zone is considered when doing time calculations, e.g. 10 AM CEST minus 8 AM UTC is zero.
• A datetime in MySQL does not have a zone. It just stores the literal string "2010-05-01 12:00:00".
• That means that Rails must make assumptions about timestamps loaded from and written to MySQL.

Rails has two completely different modes …

This is an extension to PostgreSQL vs MySQL: How to UPDATE using a JOIN.

UPDATE employees
SET department_name = departments.name,
  department_area = areas.name
FROM departments, areas
WHERE employees.department_id = departments.id
AND departments.id = areas.department_id

Understanding your type of cronjob

Some cronjobs must only run on a single server. E.g. when you run nightly batch operations on the database, it should probably run on a single server. Running it on multiple servers would likely result in deadlocks or corrupt data.

Some cronjobs must always run on all servers. E.g. starting a sidekiq process on reboot.

Configuring whenever

If not configured otherwise, cronjobs defined in whenever's `s…

Katapult 0.3.0 brings Rails 5 and Ruby 2.5 support with a new design, plus a ton of smaller features, fixes and improvements.

Features

• Generating a Rails 5.1.4 app on Ruby 2.5.0
• Dropped asset pipeline in favor of Webpacker
• The generated application now has a sleek, simple design based on Bootstrap
• Employing Unpoly
• New application model DSL shortcut crud for "create a model and a web UI with crud actions"
• The generated application model is now a transformable e…

This cucumber step is useful for testing an image (looking at the src of the image).

Then(/^I should see the image "([^"]*)"$/) do |filename_with_extension|
  expect(page).to have_css("img[src*='#{filename_with_extension}']")
end

Then I should see the image "placeholder.png"

Outline: Read more about how to test a uploaded file here, e.g. file downloads.