tl;dr
The
:is()pseudo selector - specificity of its most specific argument - matches against a comma-separated list of selectors.
Compound selectors like ...
.datepicker .prev, .datepicker .next, .datepicker .switch
padding-bottom: 1rem
ul li, ol li
list-style-type: none
can be simplified by using the :is() pseudo selector ...
.datepicker :is(.prev, .next, .switch)
padding-bottom: 1rem
:is(ul, ol) li
list-style-type: none
Hint
The specificity of
:is()is equals t...
tl;dr
The
:where()pseudo selector - zero specificity - matches against a comma-separated list of selectors.
Compound selectors like ...
.datepicker .prev, .datepicker .next, .datepicker .switch
padding-bottom: 1rem
ul li, ol li
list-style-type: none
can be simplified by using the :where() pseudo selector ...
.datepicker :where(.prev, .next, .switch)
padding-bottom: 1rem
:where(ul, ol) li
list-style-type: none
Hint
The specificity of
:where()is always zero!I...
Don't sum up columns with + in a sql-query if NULL-Values can be present.
MySQL and PostgreSQL cannot sum up NULL values with the + value. The sum value will be NULL.
MySQL:
mysql> select 1 + 2 + 3;
+-----------+
| 1 + 2 + 3 |
+-----------+
| 6 |
+-----------+
1 row in set (0,00 sec)
mysql> select 1 + NULL + 3;
+--------------+
| 1 + NULL + 3 |
+--------------+
| NULL |
+--------------+
1 row in set (0,00 sec)
Postgres:
test_database=# select 1 + 2 + 3;
?column?
----------
6
(1 row)
t...
This is a small example on how you can check if your Postgres index can be used by a specific query in you Rails application. For more complex execution plans it might still be a good idea to use the same path of proof.
query = User.order(:last_name, :created_at).to_sql
puts query
# => SELECT "users".* FROM "users" ORDER BY "users"."last_name" ASC, "users"."created_at" ASC
add_index :users, [:last_name, :created_at]
```...
If you want to have an English Ubuntu UI, but still see dates, money amounts, paper formats, etc. in German formats, you can fine-tune your /etc/default/locale like this:
LANG="en_US.UTF-8"
LC_CTYPE="de_DE.UTF-8"
LC_NUMERIC="de_DE.UTF-8"
LC_TIME="de_DE.UTF-8"
LC_COLLATE="de_DE.UTF-8"
LC_MONETARY="de_DE.UTF-8"
LC_PAPER="de_DE.UTF-8"
LC_NAME="de_DE.UTF-8"
LC_ADDRESS="de_DE.UTF-8"
LC_TELEPHONE="de_DE.UTF-8"
LC_MEASUREMENT="de_DE.UTF-8"
LC_IDENTIFICATION="de_DE.UTF-8"
Make sure you have both en...
If validations failed for a record, and you want to find out if a specific validation failed, you can leverage ActiveModel's error objects.
You rarely need this in application code (you usually just want to print error messages), but it can be useful when writing tests.
As an example, consider the following model which uses two validations on the email attribute.
class User < ApplicationRecord
validates :email, presence: true, uniqueness: true
end
Let's assume we have a blank user:
user = Us...
When your Rails application offers downloading a bunch of files as ZIP archive, you basically have two options:
This card is about option 2, and it is actually fairly easy to set up.
We are using this to generate ZIP archives with lots of files (500k+) on the fly, and it works like a charm.
Offering downloads of large archives can be cumbersome:
Recently we detected a memory leak in one of our applications. Hunting it down, we found that the memory leak was located in Rails' #prepend_view_path. It occurs when the instance method prepend_view_path is called in each request, which is a common thing in a multi-tenant application.
On top of leaking memory, it also causes a performance hit, since templates rendered using the prepended view path will not be cached and compiled anew on each requqest.
This is not a new memory leak. It was [first reported in in 2014](https://github.com...
Add a custom maintenance page for each vhost. We have automated this with capistrano 3.x, but you can do it manually by following the instructions at the bottom:
Add this line to your application's Gemfile:
gem 'capistrano', '~> 3.0'
gem 'capistrano-maintenance', '~> 1.0'
Add this line to you application's Capfile:
require 'capistrano/maintenance'
Present a maintenance page to visitors. Disables your application's web interface by writing a #{maintenance_basename}.html file to each web ...
Around will not happen until after a feature's Background has been processed. Use Before and After to avoid that.
Consider this Cucumber feature file:
Feature: Something that needs to be tested
Background:
Given a user
And I sign in
Scenario: Sign out
When I sign out
Then I should see "Signed out"
Scenario: Something else
# ...
Now, assume you have these step definitions:
Around do
puts "** Around: before yield"
...
In the DevTools settings, there's a "Shortcuts" section. Found these keyboard shortcuts there:
Toggle drawer
Show console in drawer
Change number by 10
Change number by 100
Toggle "visibility:hidden!important" (useful when debugging page repaint times)
Don't show the yellow dimensions tooltip (useful when the tooltip covers just the area you need to see).
The linked content includes a few design patterns implemented with Ruby on Rails.
What is the card indented to achieve?
Included Design Patterns: Service, Value objec...
These are the results of the "personal tech stack survey". I've included only the most popular mentions, maybe it can help you find one or two useful tools for your own usage.
pie title Desktop environment
"Gnome" : 16
"i3": 2
"sway": 2
"awesome": 1
"bspwm": 1
"mate": 1
"xfce": 1
Gnome dominates (unsuprising, it's the Ubuntu default), but quite a few people use tiling window managers, most popular i3 Archive and the mostly i3-compatible [sway](https://swaywm....
This should be fixed in the latest LTS-branches of our mysql2 fork Archive , 0.2.x-lts and 0.3.x-lts.
Use
gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.2.x-lts' # for Rails 2.x
gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.3.x-lts' # for Rails 3.x
in your Gemfile, and do a
bundle update mysql2
mysql2 used to check that the client library used at runtime actually matches the one it was compiled against. However, at least on Ubunt...
To read the Rails session from a Rack middleware, use env['rack.session']. It's an ActionDispatch::Request::Session object.
class MyMiddlware
def initialize(app)
@app = app
end
def call(env)
status, headers, body = @app.call(env)
session = env['rack.session']
Rails.logger.info("Value of session['foo'] is: " + session['foo'].inspect)
[status, headers, body]
end
end
You may not be able to write to the session this way (I haven't tested this).
An end-to-end test (E2E test) is a script that remote-controls a web browser with tools like Selenium WebDriver. This card shows basic techniques for fixing a flaky E2E test suite that sometimes passes and sometimes fails.
Although many examples in this card use Ruby, Cucumber and Selenium, the techniques are applicable to all languages and testing tools.
Your tests probably look like this:
When I click on A
And I click on B
And I click on C
Then I should see effects of C
A test like this works fine...
Sometimes you want git to ignore certain files that appear on your machine. You can do this in 3 ways:
.gitignore file.gitignore entriesWhile it might be tempting to set it per project (other devs might benefit from it), you
.gitignore file with stuff...Calling bundle update (without arguments) updates all your gems at once. Given that many gems don't care about stable APIs, this might break your application in a million ways.
To stay sane, update your gems using the applicable way below:
Update the entire bundle regularily (e.g. once a week). This ensures that your libraries are up-to-date while it's easy to spot major version bumps which may break the app.