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 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...

We used zeroclipboard.js in some of our projects but now we switched to clipboard.js because it does not rely on flash. Flash support of the major browsers has ended.

Some more advantages of clipboard.js:

• it consists only of a single javascript file, so it does not trigger additional requests with rails
• it automagically provides user feedback by selecting the text it has copied
• it provides callbacks for success and error which make it easier to add custom behaviour after copying to the clipboar...

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
--------------...

Instantiating ActiveRecord objects comes expensive. To speed up things, you can choose a more direct way to talk to your database: the ActiveRecord::ConnectionAdapters::DatabaseStatements module.

Using the module and its methods is not suggested in the usual in-app workflow, as validations, callbacks, custom getters/setters etc. are ignored. However, for database-centered stuff like migrations, these fill the gap between writing pure SQL and full...

When working with custom transactions and use ActiveRecord::Rollback you may encounter unexpected behaviour if you try to roll back your changes.

tl;dr

When using nested transactions, ActiveRecord::Rollback might not do what you expect, since it will only roll back the inner, but not the outer transaction.

You can fix this behavior by using transaction(joinable: false) but this leads to a bunch of different problems.

When you don't need an explicit ActiveRecord::Rollback, don't worry about any of this and just use a plan `tran...

You can have a command repeatedly executed and the output displayed. This is useful e.g. for monitoring file system changes with ls, but has many more applications.
The update frequency is controlled by the -n argument (default: 2s), which is locale-specific; i.e. you might need to use a comma as delimiter.

  > watch -n 1.5 ls

If you want to find the commits that touched a specific text in a file, use

git log -S 'text in the code' -- path/to/file

If you use tig you may run a similar command to get a navigatable list of affected files:

tig -S'text in the code'

Example

Here is an example, where the move of the convert_number_column_value(value) method in active record is traced (simplified output):

git log -n 1 --pretty=oneline -S 'convert_number_column_value(value)' -- activerecord/lib/active_record/base.rb
ceb33f84933639d3b6...

#reverse_order does not work with complex sorting constraints and may even silently create malformed SQL for rails < 5.

Take a look at this query which orders by the maximum of two columns:

Page.order('GREATEST(pages.published_from_de, pages.published_from_en) DESC').to_sql
# => SELECT "pages".* FROM "pages" ORDER BY GREATEST(pages.published_from_de, pages.published_from_en) DESC

Rails 4

Rails 4 will not immediately raise but creates malformed SQL when trying to use reverse_order on this query:

Pageorder('GRE...

Rails 5 / 6 / 7

1. Sometimes you have search entries in the autocomplete of the address bar, which are higher weighted than your bookmarks. Pressing SHIFT + DEL while searching removes them from the history immediately.

2. Sometimes you have search entries in the autocomplete of the address bar, which are all higher weighted than your recently visited sites. Add a search for your history, so you can get recent results first.

...

You might get the above error message when cloning certain git repositories (for example the rails repository). It indicates that there is a malformed timestamp in some commit, and your git installation is configured to validate it.

As a workaround, you can disable the validation using

git config --global fetch.fsckobjects false

This settings seems to be the default for most git installations anyways.

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...

Same requests are recorded only once in vcr. Replaying a test fails, if you trigger the same request multiple times. The error message is somehow confusing, as your cassette contains the request:

An HTTP request has been made that VCR does not know how to handle

If you want to allow to match a request multiple times, you need to configure this explicit with allow_playback_repeats: true. Some exa...

Rails 5 migration classes look like this now:

class CreateUsers < ActiveRecord::Migration[5.0]

Mind the [5.0] at the end.

They do this to evolve the ActiveRecord::Migration API without breaking your historical migrations in db/migrate.

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....

You know those helper methods that just render some HTML but look weird because of content_tags all over the place? You could also use Haml instead.

Example

Consider the following helper.

def greeting
  message = ''.html_safe
  message << 'Welcome to '
  message << content_tag(:span, Rails.env, class: 'greeting--location')
  content_tag :div, message, class: 'greeting'
end

That looks clumsy and is hard to read.

Wouldn't it be nicer to say something like this?

def greeting
  render_haml <<-HAML
 ...

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...

If you were using Dusen for its query parsing and LIKE queries, we recommend to migrate to Minidusen, which extracts those parts from Dusen. Minidusen is compatible with MySQL, PostgreSQL and Rails 3.2, 4.2 and 5.0.

If you are looking for a full text indexing solution, we recommend to use PostgreSQL with pg_search.

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...

You want Spring for super-fast binstubs like bin/rails or bin/rspec which avoid Rails boot time.
You want parallel_tests to speed up full test runs of large test suites.

Unfortunately, you do not want parallel_tests to use your Spring binstubs as those parallelized tests will share data and/or loose some information. There are some issues about this on GitHub and there is a suggested [workaround](https:...

Promises are the new way™ to express "Do this, and once you're done, do that". In contrast to callbacks, promises are easily chainable. From the readme of Q, an early implementer of the pattern:

The callback approach is called an “inversion of control”. A function that accepts a callback instead of a return value is saying, “Don’t call me, I’ll call you.”. Promises un-invert the inversion, cleanly separating the input arguments from control flow arguments. This simplifies the use and creation of APIs, p...