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Updated: Jasmine: Expecting objects as method invocation arguments

Added that toEqual() also works with partial matchers:

expect(value).toEqual(jasmine.any(String))
Repeats

Don't mix Array#join and String#html_safe

You cannot use Array#join on an array of strings where some strings are html_safe and others are not. The result will be an unsafe string and will thus be escaped when rendered in a view:

unsafe_string = '<span>foo</span>'
safe_string = '<span>bar</span>'.html_safe
[unsafe_string, safe_string].join(' ') # will incorrectly render as '&lt;span&gt;foo&lt;/span&gt;&lt;span&t;bar&lt;/span&gt;'

Bad

The solution is not to call html_safe on the joined array and if you thought it would be, you [don't understand how XSS protecti...

Ruby: Using the pry debugger in projects with older Ruby versions

In case you want to use pry with an older version of Ruby, you can try the following configurations.

Ruby 1.8.7

Your pry version must not be greater than 0.9.10.

gem 'pry', '=0.9.10'
gem 'ruby-debug'
gem "ruby-debug-pry", :require => "ruby-debug/pry"
gem 'pry-nav'
gem 'ruby18_source_location'

Ruby 1.9.3

Your pry version must not be greater than 0.9.9.

gem 'debugger', '=1.1.4'
gem 'pry-debugger', '=0.2.0'
gem 'pry', '=0.9.9'

Known errors

No source for ruby-1.9.3-p551 p...

Linked content

The ultimate guide to Ruby timeouts

An unresponsive service can be worse than a down one. It can tie up your entire system if not handled properly. All network requests should have a timeout.

Here’s how to add timeouts for popular Ruby gems. All have been tested. You should avoid Ruby’s Timeout module. The default is no timeout, unless otherwise specified. Enjoy!

Linked contentAuto-destruct in 53 days

Updated: RSpec: How to define classes for specs

Added section 2 with the guide of using stub_constant as an alternative to the variant with a variable in section 3.

Linked contentAuto-destruct in 52 days

Updated: Don't mix Array#join and String#html_safe

Added the updated part for Rails > 3, which suggests the use of ActionView's safe_join method.

Repeats

How DECIMAL columns deal with numbers exceeding their precision or scale

When storing floating-point numbers such as prices or totals in an SQL database, always use a DECIMAL column. Never use FLOAT or kittens will die.

DECIMAL columns are parametrized with a precision and a scale. These parameters describe which numbers can be stored in that column. E.g. a decimal with a precision of 5 and a scale of 2 can store numbers from -999.99 to 999.99, but not 1000 or 1.234.

This card explains what various databases do when you try to store a number in a DECIMAL field, and that number exceeds that colum...

Repeats

simple_format does not escape HTML tags

simple_format ignores Rails' XSS protection. Even when called with an unsafe string, HTML characters will not be escaped or stripped!

Instead simple_format has a whitelist of tags it allows. These are:

ActionView::Base.sanitized_allowed_tags
=> #<Set: {"small", "dfn", "sup", "sub", "pre", "blockquote", "ins", "ul", "var", "samp", "del", "h6", "h5", "h4", "h3", "h2", "h1", "span", "br", "hr", "em", "address", "img", "kbd", "tt", "a", "acronym", "ab...
Repeats

Webpacker: Configuring browser compatibility

Webpacker uses Babel and Webpack to transpile modern JavaScript down to EcmaScript 5. Depending on what browser a project needs to support, the final Webpack output needs to be different. E.g. when we need to support IE11 we can rely on fewer JavaScript features. Hence our output will be more verbose than when we only need support modern browsers.

Rails 5.1+ projects often use Webpacker to preconfigure the Webpack pipeline for us. The default configuration works something like this:

  1. Webpack checks w...

CarrierWave: How to generate versions with different file extensions

We use CarrierWave in many of our projects to store and serve files of various formats - mostly images. A common use case of CarrierWave's DSL is to "process" the original file in order to create multiple "versions", for example different resolutions of the same image.

Now we could go one step further: What if we want to create versions that have a different file extension than the original file? For example, let's assume we'd like to create a ve...

Repeats

Ruby: Referencing global variables with the built-in English library

With Ruby's build-in library English you can reference global variables with an english name. This makes you code easier to read and is also suggested by Rubocop's Style/GlobalVars cop.

Example before:

if 'foo' =~ /foo/
  puts $~[1] # => foo
end

Example after:

if 'foo' =~ /foo/
  puts $LAST_MATCH_INFO[1] # => foo
end

Require pitfall in Rails

The English library is not loaded by default in Rails. S...

Linked contentAuto-destruct in 46 days

Updated: Inspecting a live Ruby process

Updated the gdb-inspect card with instructions for Ruby 2.4+.

Ruby 2.4+

TL;DR live inspection:

# First, find out the PID of your Ruby process (e.g. passenger-status)
$ gdb PID
(gdb) generate-core-file                  # generate core.PID file for later inspection
(gdb) t a a bt                            # thread apply all backtrace
(gdb) call (void) close(1)                # close the existing file descriptors for std...
Deprecated

How Rails and MySQL are handling time zones

When working with times and dates in Rails applications, you need to deal with the following problem:

  • In Rails, Time objects have a time zone. You can get the zone name by doing time_object.zone.
  • This zone is considered when doing time calculations, e.g. 10 AM CEST minus 8 AM UTC is zero.
  • A datetime in MySQL does not have a zone. It just stores the literal string "2010-05-01 12:00:00".
  • That means that Rails must make assumptions about timestamps loaded from and written to MySQL.

Rails has two completely different modes ...

Deprecated

You don't need each, collect or select in Coffeescript

Working with lists in Javascript is painful because the native Array class is so poorly designed.

One way to reduce the pain is to to use Underscore.js's functions like _.each, _.map or _.select, which unfortunately clutters your code with awkward calls to the _ helper.

Fortunately when you use CoffeeScript you don't need any of that. CoffeeScript has a very versatile for keyword that can do anything that each, collect or select can do. Enjoy!

each

f...
Linked contentAuto-destruct in 40 days

Updated: Ruby / Rails: clone vs. dup vs. deep_dup

Clarified that deep_dup is only implemented on Hash and Array.

Object#deep_dup calls dup which does not deep_dup its attributes / instance variables.

Linked contentRepeats

count vs. size on ActiveRecord associations

TLDR

  • When counting records in an association, you should use #size in most cases.
  • It will not work if the parent record has never been saved. Also there are finer distinctions between #size and #count. See below.

count

  • Always makes a COUNT(*) query if a counter cache is not set up.
  • If a counter cache is set up on the association, #count will return that cached value instead of executing a new query.

size, if the association has already been loaded

  • Counts elements in the already loaded array.
  • Does not ...
Linked contentAuto-destruct in 37 days

Updated: FactoryBot: How to get the class from a factory name

FactoryBot.factory_by_name is deprecated. Card has been updated with the current solution.

Repeats

How Ruby method lookup works

When you call a method on an object, Ruby looks for the implementation of that method. It looks in the following places and uses the first implementation it finds:

  1. Methods from the object's singleton class (an unnamed class that only exists for that object)
  2. Methods from prepended modules (Ruby 2.0+ feature)
  3. Methods from the object's class
  4. Methods from included modules
  5. Methods from the class hierarchy (superclass and its ancestors)

Example

Let's say we h...

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