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Repeats

Don't assign time values to date attributes

Do not pass times to date attributes. Always convert times to dates when your application uses time zones.

Background

A time-zoned Time attribute on a Rails record is converted to UTC using to_s(:db) to be stored, and converted back into the correct time zone when the record is loaded from the database. So when you are not on UTC, time objects will be converted as follows.

>> Time.current
=> Fri, 15 Mar 2013 11:56:03 CET +01:00
>> Time.current.to_s(:db)
=> "2013-03-15 10:56:03" # This is now UTC

Problem

That will…

Repeats

FileIO: Writing strings as Carrierwave uploads

When you have string contents (e.g. a generated binary stream, or data from a remote source) that you want to store as a file using Carrierwave, here is a simple solution.

While you could write your string to a file and pass that file to Carrierwave, why even bother? You already have your string (or stream).
However, a plain StringIO object will not work for Carrierwave's ActiveRecord integration:

>> Attachment.create!(file: StringIO.new(contents))
TypeError: no implicit conversion of nil into String

This is because Carrierwave ex…

Repeats

MySQL: Disable query cache for database profiling

If you want to see how long your database queries actually take, you need to disable MySQL's query cache. This can be done globally by logging into a database console, run

SET GLOBAL query_cache_type=OFF;

and restart your rails server.

You can also disable the cache on a per query basis by saying

SELECT SQL_NO_CACHE * FROM ...

You also probably want to disable Rails internal (per-request) cache. For this, wrap your code with a call to ActiveRecord::Base.uncached. For example, as an around_filter:

def disable_cache  ...
External contentRepeats

Rails SQL Injection Examples

This page lists many query methods and options in ActiveRecord which do not sanitize raw SQL arguments and are not intended to be called with unsafe user input. Careless use of these methods can open up code to SQL Injection exploits. The examples here do not include SQL injection from known CVEs and are not vulnerabilites themselves, only potential misuses of the methods.

Please use this list as a guide of what not to do.

Unfinished

Advantages of using appname.vcap.me:3000 over localhost:3000

Running rails server will start a local server that you can access via http://localhost:3000.

When you are working on multiple web apps, they will likely cookies with generic names on localhost. This is annoying, since you will sign out your current user whenever you switch to another app.

A better way is to use the vcap.me service. All vcap.me subdomains resolve to your local IP (127.0.0.1). That means you can use a different hostname for different apps, and you will stay logged in in each app:

```text
http://foo-app.vcap.me:3000 =…

Repeats

How to run a small web server (one-liner)

Sometimes you just want to have a small web server that serves files to test something.

Serve the current directory

On Ruby 1.9.2+ you can do the following ("." for current directory).

ruby -run -ehttpd . -p8000

Python 2.x offers a similar way.

python -m SimpleHTTPServer 8000 .

This is the same way with Python 3.x

python -m http.server

In both cases your web server is single-threaded and will block when large files are being downloaded from you.

For solutions in many other languages, see the [big list of http s…

Repeats

Rails: Adding view paths on the fly

Rails offers a way to prepend (or append) view paths just for the current request.

Example

A use case of this is a different set of view templates that should be used under certain circumstances:

class UsersController < ApplicationController

  before_action :prepare_views
  
  def index
    ...
  end    
  
  private
  
  def prepare_views
    if <condition>
      prepend_view_path Rails.root.join('app', 'views', 'special')
    end
  end
  
end

If <condition> is true, Rails will first look into app/views/special to find a…

Upgrading a Rails app to Cucumber 3

Upgrade gems

You need to update a lof gems. Make sure you don't have any version constraints in your Gemfile or your bundle update won't do anything!

Upgrade cucumber_priority:

bundle update cucumber_priority

Upgrade spreewald:

bundle update spreewald

Upgrade cucumber_factory:

bundle update cucumber_factory

Upgrade parallel_tests:

bundle update parallel_tests

Even on the latest version, parallel_tests will print some deprecation warnings due to using an older formatter A…

Delegating an instance method to a class method in Ruby

With ActiveSupport you can say:

class Robot
  def self.likes_humans?
    'Nope.'
  end

  delegate :likes_humans?, to: :class
end

Robot.likes_humans?
# => 'Nope.'

Robot.new.likes_humans?
# => 'Nope.'
Repeats

Grep through the DOM using the Capybara API

When your Cucumber feature needs to browse the page HTML, and you are not sure how to express your query as a clever CSS or XPath expression, there is another way: You can use all and find to grep through the DOM and then perform your search in plain Ruby.

Here is an example for this technique:

Then /^I should see an image with the filename...

VNC browser disappears while typing

We often use the Then console step from spreewald in combination with geordi vnc from geordi to debug tests within a real browser. Sometimes when you type in the browser it suddenly disappears. You will only see a grey screen then.

This will always happen if you press the d key. Press the d key again and the browser will appear again.

Firefox: Focus-sensitive Selenium tests do not work reliably in parallel test execution

This is a problem when using Selenium with Firefox. We recommend using ChromeDriver for your Selenium tests.


Firefox will not trigger focus/blur events when its window is not focused. While this makes sense in standard usage, it breaks in parallel test execution.

Please do not rely on focus events in your tests. The linked card has an example of how to build passing tests that deal with focus/blur events.

Making httpclient use the operating system's SSL cert store

The httpclient gem comes with a custom SSL cert store.

While an customizable, application-level cert store is great when you need to deal with broken or self-signed certificates, you usually want to use the cert store from the underlying Linux. The Linux cert store is updated periodically while httpclient's cert store goes out of date and will eventually not be able to verify certs.

To use the cert store from the underlying operating system:

```ruby
client = HTTPClient.new
client.ssl_config.cert_store…

Repeats

RSpec: be_true does not actually check if a value is true

Don't use be_true to check if a value is true. It actually checks if it anything other than nil or false. That's why it has been renamed to be_truthy in recent RSpec versions.

The same thing holds for be_false, which actually checks if a value is not "truthy".

If you want to check for true or false in RSpec 2, write this instead:

value.should == true
value.should == false

If you want to check for true or false in RSpec 3+, write this instead:

```
expec…

Legacy docs for Font Awesome 4.7

See the attached link for a list of icons in Font Awesome 4.

Icon names work differently in Font Awesome 5, where a name is only valid in combination with a name of the icon set.

External contentRepeats

Installing multiple MySQL versions on the same Linux with mysql-sandbox

Ubuntu has a package mysql-sandbox that lets you install multiple MySQL versions into your user home:

sudo apt install mysql-sandbox
# Download mysql distribution .tar.gz from mysql.com
# You must choose "Generic Linux" instead of "Ubuntu" so you get a .tar.gz instead of .deb
make_sandbox mysql-5.7.21-linux-glibc2.12-x86_64.tar.gz

On older distributions, make_sandbox might be mysql_sandbox instead.

This will install this version into /~/sandboxes/msb_5_7.21. The folder includes a command to start the MySQL daemon for that …

Repeats

Showing a custom maintenance page while deploying

Add a custom maintenance page for each vhost (require capistrano 3.x):

Installation

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'

Enable task

Present a maintenance page to visitors. Disables your application's web interface by writing a #{maintenance_basename}.html file to each web server. The servers must be configured to detect the presence of this file, and if it i…

Nested Spreewald patiently blocks are now patient

In Spreewald 1.10.4+, nested patiently blocks are now patient.

Here is an example:

patiently do
  outer_code
  patiently do
    inner_code
  end
end

On spreewald 1.11.2+ the inner block will wait for the full configured wait time (by default 5 seconds). The outer patiently block would now be out of time, but it will always be retried at least a second time.

In versions 1.10.4 - 1.11.1, inner blocks would keep giving the outer block additional time to finish, which solves the same issues, but as a downside can cause the wh…

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