This card will show you a cool way to define a class using Struct.new.
A common usecase for Structs are temporary data structures which just hold state and don't provide behaviour. In many cases you could use a simple hash as a data structure instead. However, a Struct provides you with a nice constructor, attribute accessors and complains if you try to access undefined attributes. Structs are easy to compare (by attributes). A struct gives meaning to the data.

Disclaimer

Structs are great...

Rails default config uses the ActiveSupport::Cache::NullStore and disables controller caching for all environments except production:

config.action_controller.perform_caching = false
config.cache_store = :null_store

If you want to test caching you have at least two possibilities:

1. Enable caching for every test (not covered by this card and straightforward)
2. Enable caching for individual test

Enable caching for individual test (file cache)

1. Leave the default c...

Shoulda Matchers don't provide canditional validations (validations with if: option). Here is how to write tests for the condition:

Class:

class Employee < ActiveRecored::Base
  validates :office, presence: true, if: manager?
  
  def manager?
    ...
  end
end

Test:

describe Employee do

  describe '#office' do
    
    context 'is a manager' do
      before { allow(subject).to receive(:manager?).and_return(true) }
      it { is_expected.to validate_presence_o...

When using GROUP BY, MySQL now complains if the SELECT includes columns which are not part of the GROUP BY.

Reason:

There could be multiple values for those columns per group but only one value can be picked for the results.

The default behaviour of MySQL prior to version 5.7 will not complain and arbitrarily choose a value. But this leads to non-deterministic results. So MySQL now has enabled the only_full_group_by setting by default to prevent this.

In Rails this could lead to some trouble, because scopes do not have sp...

ChromeDriver clicking works by simulating a mouse click in the middle of the element's first client rect (or bounding client rect if it doesn't have a first client rect). (Clicking issues)

So if you are trying to click on an element, chromedriver tries to click at the position where it first finds that element.

This can lead to some problems and unexpected behavior like:

• Element is not clickable at point ... erros
• Another element which is now located at...

Since Rails 5, domain models inherit from ApplicationRecord by default.

This is the place to put code that should be available in all your application's models.
There is no reason to monkey-patch ActiveRecord::Base when following that practice.

When you have a multi-server setup, you'll be adding a new server from time to time. Before doing a full deploy, you might want to test that server in an isolated deploy. There is a single way to do this: the HOSTFILTER env variable.

Commenting out "server" lines in the Capistrano deploy config will raise a Capistrano::NoMatchingServersError with <task> is only run for servers matching {:roles=> <role>}, but no servers matched. Instead, specify the server-under-test like this:

HOSTFILTER=separate-sidekiq.makandra.de cap productio...

Ubuntu might create several keyrings for you. Note that keyring passwords are initially set to the user password but do not change with it. If you can't seem to find the correct password for a keyring, try entering the inital password.

If you still can't find it, you might have to delete that keyring:

• open "Passwords and Keys" (seahorse application)
• right-click on the keyring you want to change
• press Delete

These tools help you in checking websites globally:

DNS Checker
: This tool allows for global DNS propagation checking.

GeoScreenshot
: This tool takes screenshots of a given URL from various locations across the world.

This is useful if, for example, you want to use a background-image that has to scale with the width and the div should only have the height of the picture.

html:

<div class="outer">
  <div class="inner">
  </div>
</div>

css:

.outer {
  width: 100%;
  background-image: image-url('background.png');
  background-size: cover;
}
  
.inner {
  padding-top: 60%;
}

How does it work?

There are several CSS attributes that can handle values as percentage. But they use different other attributes as "reference value...

Webmocks hash_including is similar to RSpec::Mocks::ArgumentMatchers#hash_including. Be aware that hash_including (webmock v3.0.1) doesn't parse integer values to String.

Without hash including you would say:

uri = URI('http://example.com/?foo=1&bar=2')
stub_request(:get, 'example.com').with(query: {foo: 1, bar: 2})
Net::HTTP.get(uri) # ===> Success

If you only want to check if foo is present you can use hash_including:

uri = URI('http://example.com/?foo=1&bar=2')
stub_request(:get, 'example.com').with(query: hash_i...

You can use gem list to list all gems available from a remote gem server:

gem list -r --clear-sources -s 'https://user:password@gemserver.tld/'

This is useful to debug cases where Bundler complains of a gem existing in more than one gem source.

If you stub a method or set expectations with should_receive these stubbed methods may also yield blocks. This is handy if the returning object is receiving a block call.

Consider this, where you cannot say and_return [] because of the block:

def crawl_messages
  Message.find_in_batches do |messages|
    messages.each(&:crawl)
  end
end

It works similar to and_return -- just use and_yield:

describe '#crawl_messages' do
  it 'should proc...

By default Middleman generates files with a .html extension. Because of this all your URLs end in /foo.html instead of /foo, which looks a bit old school.

To get prettier URLs, Middleman lets you activate :directory_indexes in config.rb. This makes a directory for each of your pages and puts a single file index.html into it, e.g. /foo/index.html. This lets you access pages with http://domain/foo.

Don't double your requests!

Unfortunately you are now forcing every br...

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...

Sometimes, through some firewall or proxy misconfiguration, you might have to deploy to a server that cannot access the git repository.

Solution 1: HTTP Proxy (this is the preferred fix)

SSH can be tunneled over an HTTP Proxy. For example, when the repo is on github, use this:

1. Install socat

2. Add a ~/.ssh/config on the target server(s) with permission 0600 and this content:

   Host github.com ssh.github.com
     User git
     Hostname ssh.github.com
     Port 443
     ProxyCommand socat - PROXY:<your proxyhost>:%h:%p,...
   

Dump this method into your Ruby console to quickly print data in columns. This is helpful for e.g. comparing attributes of a set of Rails records.

def tp(objects, *method_names)
  terminal_width = `tput cols`.to_i
  cols = objects.count + 1 # Label column
  col_width = (terminal_width / cols) - 1 # Column spacing

  Array(method_names).map do |method_name|
    cells = objects.map{ |o| o.send(method_name).inspect }
    cells.unshift(method_name)

    puts cells.map{ |cell| cell.to_s.ljust(col_width) }.join ' '
  end

  nil
end

Usag...