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...

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...

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...

This article will show you how to use throw and catch. It's a nice tool to break out of multiple loops when a result is obtained.

Also see our card Ruby: A small summary of what return, break and next means for blocks.

This error is raised because your old database does not have a configured environment yet, which Rails 5 enforces.

If this error occurs while migrating your parallel test databases, make sure to update the parallel_tests gem first: current versions fix this. If you're still using Cucumber < v3, the latest version of parallel_tests will be 2.18.0.

Rails applications and ruby gems should have a README that gives the reader a quick overview of the project. Its size will vary as projects differ in complexity, but there should always be some introductory prose for a developer to read when starting on it.

Purpose

That's already the main purpose of a project README: Give a new developer a quick overview of the project. In sketching this outline, the README should notify the reader of any peculiarity he needs to know of.

Remember that in a few months, you'll be a kind of "new ...

When writing XLSX files, there are gems like rubyXL or axlsx. While they do offer features like formatting or graphs, to represent spreadsheet cells, they have to keep several Ruby objects in memory. When writing huge files, both will become slow and consume lots of memory.

Enter Xlsxtream, a Ruby XLSX library with less features (e.g. no individual cell styles) but which does away with the memory issue by streaming ...

PostgreSQL supports the SQL OVERLAPS operator. You can use it to test if two date ranges overlap:

=> SELECT ('2001-02-16'::date, '2001-12-21'::date) OVERLAPS
          ('2001-12-20'::date, '2002-10-30'::date);

overlaps
--------
true

An important caveat is that the date ranges are defined as start <= time < end. As such the later date is not included in the range:

=> SELECT ('2001-02-16'::date, '2001-12-21'::date) OVERLAPS
          ('2001-12-21'::date, '2002-10-30'::date);

overlaps
--------
false

Also compar...

Summary: Don't add chromedriver-helper to the Gemfile

• the executables might break your tests in projects where chromedriver-helper is not in the Gemfile
• developers with different chrome versions will have problems using the same chromedriver-helper version

Background

If you install the chromedriver-helper gem, but don't have it in you Gemfile, your selenium tests might fail with:

Selenium::WebDriver::Error::WebDriverError: unable to connect to chromedriver 127.0.0.1:9515

The reason is that chromedriver-helper ov...

When attempting to update RubyGems, depending on updates your previously performed, you might run into an error

ERROR:  While executing gem ... (TypeError)
can't convert nil into String

Fix this by running

gem uninstall rubygems-update -a -x

A common pattern in Ruby is to to require all files in a specific diretory, using something like

Dir.glob(Rails.root.join('lib/ext/**/*.rb')).each do |filename|
  require filename
end

However, this causes files to be required in an order determined by the file system. Since load order can be important, this may lead to different behavior on different machines which are hard to debug.

Simply add a .sort:

Dir.glob(Rails.root.join('lib/ext/**/*.rb')).sort.each do |filename|
  require filename
end

Ruby 3

...

Checking if a JavaScript value is of a given type can be very confusing:

• There are two operators typeof and instanceof which work very differently.
• JavaScript has some primitive types, like string literals, that are not objects (as opposed to Ruby, where every value is an object).
• Some values are sometimes a primitive value (e.g. "foo") and sometimes an object (new String("foo")) and each form requires different checks
• There are three different types for null (null, undefined and NaN) and each has different rules for...

If you already selected an element and want to get its parent, you can call find(:xpath, '..') on it.

To get the grand-parent element, call find(:xpath, '../..').

Example

Find a link which contains a twitter icon and check that it links to the correct page:

<a href="http://twitter.com/">
  <i class="icon is-twitter"></i>
</a>

link = page.find("a .icon.is-twitter").find(:xpath, '..')
expect(link[:href]).to eq("http://twitter.com/")

About XPath

There is a good overview on XPath syntax on [w3schools](htt...

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.

Why tests are flaky

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...

Slides for Henning's talk on Sep 21st 2017.

Understanding sync vs. async control flow

Talking to synchronous (or "blocking") API

print('script start')
html = get('/foo')
print(html)
print('script end')

Script outputs 'script start', (long delay), '<html>...</html>', 'script end'.

Talking to asynchronous (or "evented") API

print('script start')
get('foo', done: function(html) {
  print(html)
})
print('script end')

Script outputs 'script start', 'script end', (long ...

TL;DR: Bundler 2.0 will rename Gemfile to gems.rb and Gemfile.lock to gems.locked (sic).

The old filenames will be supported until the release of Bundler 3.0.

Some more breaking changes here.

RSpec allows defining methods inside describe/context blocks which will only exist inside them.
However, classes (or any constants, for that matter) will not be affected by this. If you define them in your specs, they will exist globally. This is because of how RSpec works (short story: instance_eval).

Negative example:

describe Notifier do
  class TestRecord < ApplicationRecord # DO NOT do this!
    # ...
  end
  
  let(:record) { TestRecord.new }
  
  it { ... }
end

# TestRecord will exist here, outside of the spec!

D...

There are several gems that make it easy to read and process xlsx files. Parsing the entire file at once however is error-prone since each cell is transformed to a ruby object - sometimes including thousands of formatted but empty cells.

As of today, I found two promising alternatives that provide a stream-based access to spradsheet rows:

• Roo supports multiple spreadsheet types like ODS or CSV and has a quite large contributor base
• [Creek](https://github.com/pythonicrubyis...

Summary

• Use return to return from a method. return accepts a value that will be the return value of the method call.
• Use break to quit from a block and from the method that yielded to the block. break accepts a value that supplies the result of the expression it is “breaking” out of.
• Use next to skip the rest of the current iteration. next accepts an argument that will be the result of that block iteration.

The following method will serve as an example in the details below:

def example
  puts yield
  puts ...

I frequently find myself needing a combination of group_by, count and sort for quick statistics. Here's a method on Enumerable that combines the three:

module Enumerable

  def count_by(&block)
    group_by(&block)
      .transform_values(&:count)
      .sort_by(&:last)
      .to_h
  end
  
end

Just paste that snippet into a Rails console and use #count_by now!

Usage examples

• Number of email addresses by domain:

> User.all.count_by { |user| user.email.sub /^.*@/, '' }
=> { "sina.cn"=>2, ..., "hotmail.co...

Scope is all about where something is visible. It’s all about what (variables, constants, methods) is available to you at a given moment. If you understand scope well enough, you should be able to point at any line of your Ruby program and tell which variables are available in that context, and more importantly, which ones are not.

The article gives detailed explanation on the variable scope in ruby with examples that are easy to understand. Every ruby developer should at least know the first part of the article by heart. The second half ...

You can use local copies of gems in your Gemfile like this:

gem 'spreewald', path: '~/gems/spreewald'

As soon as you have bundled your project with the local copy of the gem, all code changes in the copy will be available on your project. So you can for example set a debugger or add console output in the gem and use it from your project.
If you checked out the gem with your versioning tool, you can easily reset your changes afterwards or make a pull request for the gem if you improved it.

Don't commit a Gemfile with local path...

In the ruby shell (IRB) and rails console the return value of the previous command is saved in _ (underscore). This might come in handy if you forgot to save the value to a variable and further want to use it.

Example:

irb(main):001:0> 1 + 2
=> 3
irb(main):002:0> _
=> 3
irb(main):003:0> a = _
=> 3