So you're getting an error like this:

undefined method `activate_bin_path' for Gem:Module (NoMethodError)

Here is what happened:

• You installed a recent version of Rubygems
• You installed some gems that install a binary (like bundle, rake or rails) with code that only works with modern Rubygems versions
• You downgraded Rubygems to an older versions, which doesn't change any binaries
• When calling binaries with the old Rubygems version, it cannot process the line Gem.activate_pin_path(...) that was written out by th...

TL;DR: Update the 'net-ssh' gem by adding to your Gemfile:

gem 'net-ssh', '=2.9.1'

Now run bundle update net-ssh. It has no dependencies so it shouldn't update other gems.

If you're using Ruby 1.8.7 and want to update net-ssh to a version > 2.9.1 you also need to add this to your gemfile:

gem 'backports', :require => false

... and in your deploy.rb add this:

require 'backports/1.9.2/array/select' 

Background

You propably have an older version of Capistrano and thereby an older version of `n...

So you're getting this failure when running bundle install on an older project:

Your Gemfile.lock is corrupt. The following gems are missing from the DEPENDENCIES section: 'archive-tar-minitar' 'hoe' 'rcov'

This happens when you are using a new version of Bundler with a project that was bundled with a very old version of Bundler. For reasons unknown, the Bundler dependency API returns different dependencies for some gems (like ruby-debug or rainpress) than the dependencies found in the downloaded gemspecs. While old versi...

• Plot graphs in Ruby
• WebGraphviz renders in your browser via JavaScript (to store the rendered graph, extract the SVG using your browser's DOM inspector)
• GraphViz with DOT: Online http://graphs.grevian.org/graph https://graphviz.christine.website/ or offline https://makandracards.com/makandra/1589-auto-generate-state_machine-graphs-as-png-images
• Balsamiq
• Draw.io
• [Excalidraw](https:...

This card tries to summarize by example the different uses of heredoc.

• In Ruby << vs. <<- vs. <<~
• In Rails strip_heredoc vs. squish

strip_heredoc should be used for a text, where you want to preserve newlines. (multi-line -> multi-line)

squish should be used for a text, where you want to squish newlines. (multi-line -> one-line)

Ruby 2.3+

def foo
  bar = <<~TEXT
    line1
    line2
    line3
  TEXT
  puts bar.inspect
end
foo => "line1\nline2\nline3\n"

Read more: [Unindent HEREDOCs in Ruby 2.3](/m...

You can use three different versions of the regular expression syntax in grep:

• basic: -G
• extended: -E(POSIX)
• perl: -P (PCRE)

Difference between basic and extended:

In basic regular expressions the meta-characters '?', '+', '{', '|', '(', and ')' loose their special meaning; instead use the backslashed versions '?', '+', '{', '|', '(', and ')'.

Difference between extended (POSIX) and perl (PCRE): E.g. \d is not supported in POSIX.

This g...

Easy mode

This method will remove automatically installed packages that no other packages depend on any more. This, of course, includes obsolete kernel versions, with the explicit exception of the currently running kernel, the kernel version that was installed on the system before that and, of course, the latest updated version of the kernel. However, it will also remove any and all other packages that have been marked as installed automatically but have no other packages depending on them. This could lead to unexpected removal of packag...

When testing your command line application with Aruba, you might need to stub out other binaries you don't want to be invoked by your test.

Aruba Doubles is a library that was built for this purpose. It is not actively maintained, but works with the little fix below.

Installation

Install the gem as instructed by its README, then put this Before block somewhere into features/support:

Before do
  Arub...

A Rake task appears in rake -T if it has a description:

desc 'Compile assets'
task :compile do
  ...
end

To not list it, simply omit the description:

task :compile do
  ...
end

You can also hide a Rake task that has been defined by someone else (like a gem) by removing the description:

Rake::Task['compile'].clear_comments

Or you can whitelist which tasks should be listed:

visible_tasks = %w(compile build package)
Rake::Task.tasks.each do |task|
  visible_tasks.include?(task.name) or task.clear_comments
en...

When you're writing specs for ActiveRecord models that use memoization, a simple #reload will not do:

it 'updates on changes' do
  subject.seat_counts = [5]
  subject.seat_total.should == 5
  # seat_total is either memoized itself, or using some
  # private memoized method
  
  subject.seat_counts = [5, 1]
  subject.seat_total.reload.should == 6 # => Still 5
end

You might be tempted to manually unmemoize any memoized internal method to get #seat_total to update, but that has two disadvant...

Yesterday I stumbled across a talk in which the guy mentioned module sub-classing. I was curious what you can do with it and found his blog post with a cool example. It allows you to inject some state into the module you are including elsewhere. Check it out!

class AttributeAccessor < Module
  def initialize(name)
    @name = name
  end

  def included(model)
    super
    define_accessors
  end

  private

  def define_accessors
    ivar = "@#{@name}"
    define_writer(ivar)
    define_reader(ivar)
  end

  def define_writer(ivar)
    ...

In order to have monitoring for Sidekiq (like queue sizes, last run of Sidekiq) your application should have a monitoring route which returns a json looking like this:

{
  "sidekiq": {
    "totals": {
      "failed": 343938,
      "processed": 117649167
    },
    "recent_history": {
      "failed": {
        "2016-11-06": 1,
        "2016-11-07": 46,
        "2016-11-08": 0,
        "2016-11-09": 0,
        "2016-11-10": 0
      },
      "processed": {
        "2016-11-06": 230653,
        "2016-11-07": 230701,
        "2016-11-08"...

Closure_tree lets your ActiveRecord models act as nodes in a tree data structure.

This promises a few improvements over the battle-tested ancestry gem, such as:

• Better performance
• Pre-ordered trees (painful to do with ancestry)
• Holds a mutex during tree manipulations (an issue with ancestry, where concurrent updates can cause deadlocks and corrupt data).

It has some more moving parts than ancestry though (see below).

Implementation
--------------...

Detect if a gem has been activated

A gem is activated if it is either in the current bundle (Gemfile.lock), or if you have manually activated it using Kernel#gem (old-school).

To detect if e.g. activerecord has been activated:

if Gem.loaded_specs.has_key?('activerecord')
  # ActiveRecord was activated
end

Detect if a particular gem version has been activated

To detect if e.g. activerecord ma...

We have released a new library Gemika to help test a gem against multiple versions of Ruby, gem dependencies and database types.

Here's what Gemika can give your test's development setup (all features are opt-in):

• Test one codebase against multiple sets of gem dependency sets (e.g. Rails 4.2, Rails 5.0).
• Test one codebase against multiple Ruby versions (e.g. Ruby 2.1.8, Ruby 2.3.1).
• Test one codebase against multiple database types (currently MySQL or PostgreSQL).
• Compute a matrix of all possib...

This error can be caused by the mysql2 gem under mysterious circumstances. You need to remove it with gem uninstall mysql2 and then reinstall it (or just run bundle).

gem pristine mysql2 will not be enough.

ActiveSupport::Notifications provides an instrumentation API for Ruby. It is used throughout rails to publish instrumentation events that include information about each part of a request/response cycle.

Have a look at your application log file - yes, those are those events. The cool thing is that you can subscribe to those events.

There is also a convenience method that allows you to subscribe to those events only for the time of executing a block of code. Thus you can capture all sql queries that are triggered when executing your block....

In this article, we’ll look at what side effects are, why they are problematic despite being necessary, and how to isolate them to minimise their drawbacks.

We have a new gem Minidusen which extracts Dusen's query parsing and LIKE query functionality.

Minidusen can no longer index text in MySQL FULLTEXT columns, which was hardly used and didn't always help performance due to the cost of reindexing.

Minidusen is currently compatible with MySQL, PostgreSQL, Rails 3.2, Rails 4.2 and Rails 5.0.

Basic Usage

Our example will be a simple address book:

class Contact < ActiveRecord::Base
  validates_presence_of :name, :street, :city, :e...

Capistrano is by default configured to exclude the gems of the groups development and test when deploying to the stages production and staging. Whenever you create custom groups in your Gemfile, make sure to exclude these, if they should not be deployed to the servers. The gems of these groups might not be loaded by rails, however, the deployment process will take longer as the gems will be downloaded and installed to the server.

e.g. to exclude the groups cucumber and deploy, add the following to `config/deploy/production.rb...

Presentation about optimizing Ruby on Rails apps.

From Nico Hagenburger (homify's lead frontend developer).

Ruby's __FILE__ keyword returns the path to the current file. On popular for this are Ruby binaries:

#!/usr/bin/env ruby
$LOAD_PATH << File.expand_path('../../lib', __FILE__)
require 'my_cli'
MyCli.run!

However, if you create a symlink to this file, this will no longer work. __FILE__ will resolve to the path of the symlink, not to its target.

One solution is to use File.realpath(__FILE__).

In Ruby 2+ you can also use this:

$LOAD_PATH << File.expand_path('../lib', __dir__)

__dir__ is simply a shortcut for `...

Here is a symbol of an eight note: ♪

Its two-byte hex representation is 0x266A.

This card describes how to create a string with this symbol in various languages.

All languages

Since our tool chain (editors, languages, databases, browsers) is UTF-8 aware (or at least doesn't mangle bytes), you can usually get away with just pasting the symbol verbatim:

note = '♪'

This is great for shapes that are easily recognized by your fellow programmers.
It's not...