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Repeats

How to fix: Session hash does not get updated when using "merge!"

tl;dr: Do not use merge! for session hashes. Use update instead.

Outline

Let's assume you're modifying the Rails session. For simplicity, let's also assume your session is empty when you start (same effect when there is data):

# In our example, we're in a Rack middleware
request = Rack::Request.new(env)
request.session.merge! :hello => 'Universe'
request.session
=> {}

Wat?

Even worse: When you inspect your request.session like above (e.g. in a debugger shell, o…

Repeats

Do not rescue inline in Ruby

When you are calling a method that may raise an exception that you don't care about, you might think of doing something like this:

@user = User.power_find(something) rescue User.new

Do not do that! You will be rescuing away StandardError and all its subclasses, like NameError – meaning that even a typo in your code won't raise an error.

Instead, rescue the exception type that you are expecting:

@user = begin
  User.power_find(something)
res...

Bootstrap 4 skin for the Rome datepicker

Here is how to make Rome datepicker look like the rest of your Bootstrap 4 application.

Rome comes with very little basic styling. While we could redefine its classes, we can configure the classes Rome applies to its elements to make it look like this:

Example Image

Since Bootstrap 4 comes with several helpful utility classes, and requires fewer markup/containers, we can achieve Bootstrap 4 experience by applying a few classes via the styles setting.

You still need to include `ro…

Repeats

Rails: Passing array values to tag helpers like link_to

From at least Rails 4, the ActionView tag helper turns Array values of HTML options into a single space-separated string.
This means you can pass an array to :class options:

```
extra_classes = %w[one two]

= link_to 'Dashboard', root_path, class: ['btn', 'btn-primary', *extra_classes]
=> Dashboad

= content_tag 'div', 'Hello World', class: %w[alert alert-info]
=> <div class="alert alert-info">Hello World</div>

= …

Repeats

How to tackle complex refactorings in big projects

Sometimes huge refactorings or refactoring of core concepts of your application are necessary for being able to meet new requirements or to keep your application maintainable on the long run. Here are some thoughts about how to approach such challenges.

Break it down

Try to break your refactoring down in different parts. Try to make tests green for each part of your refactoring as soon as possible and only move to the next big part if your tests are fixed. It's not a good idea to work for weeks or months and wait for ALL puzzle pieces to…

Upgrade guide for moving a Rails app from Webpack 3 to Webpack 4

Webpacker is Rails' way of integrating Webpack, and version 4 has been released just a few days ago, allowing us to use Webpack 4.

I successfully upgraded an existing real-world Webpack 3 application. Below are notes on everything that I encountered.
Note that we prefer not using the Rails asset pipeline at all and serving all assets through Webpack for the sake of consistency.

Preparations

  • Remove version locks in Gemfile for webpacker
  • Remove version locks in package.json for webpack and webpack-dev-server
  • Install by ca…
Repeats

Running external commands with Open3

There are various ways to run external commands from within Ruby, but the most powerful ones are Open3.capture3 and Open3.popen3. Since those can do almost everything you would possibly need in a clean way, I prefer to simply always use them.

Behind the scenes, Open3 actually just uses Ruby's spawn command, but gives you a much better API.

Open3.capture3

Basic usage is

```ruby
require 'open3'

stdout_str, error_str, status = Open3.capture3('/some/binary', 'with', 'some', 'args')
if status.success?…

Repeats

Guide to localizing a Rails application

Localizing a non-trivial application can be a huge undertaking. This card will give you an overview over the many components that are affected.

When you are asked to give an estimate for the effort involved, go through the list below and check which points are covered by your requirements. Work with a developer who has done a full-app localization before and assign an hour estimate to each of these points.

Static text

  • Static strings and template text in app must be translated: Screens, mailer templates, PDF templates, helpe…

Rails: How to get URL params without routing parameters (or vice versa)

Rails' params hash contains any request parameters (URL parameters or request payload) as well as routing parameters like :controller, :action, or :id.

To access only URL parameters, use request.query_parameters. Routing params are available through request.path_parameters.

```ruby
# On /users?query=Bob&page=2

request.params
=> {"page"=>"2", "query"=>"Bob", "controller"=>"users", "action"=>"index"}

request.query_parameters
=> {"page"=>"2", "query"=>"Bob"}

request.path_parameters
=> {:controller=>"users", :action=>"i…

Auto-destruct in 36 days

Consul 1.0.1 has been released

Methods defined with power now preserve the arity of their block.

This fixes an issue with assignable_values not passing the current record to a power that takes an argument:

class Power
  include Consul::Power

  power :client_notes do |client|
    # ...
  end
end

Power.new.method(:client_notes).arity # => now 1, used to be -1
Repeats

We now have our own memoization gem "Memoized"

We forked trusty memoizer to make two changes:

  1. Memoized methods now preserve their arity. Previously all memoized methods had an arity of -1.
  2. Memoized methods are now faster at runtime. This will only be noticable if you call a memoized methods many times in the same request.

We published our fork as a new gem named memoized.

memoized is API-compatible to memoizer, you just need to include Memoized instead of `M…

Repeats

Getter and setter functions for Javascript properties

Javascript objects can have getter and setter functions that are called when a property is read from or written to.

For example, if you'd like an object that has a virtual person.fullName attribute that dynamically composes person.firstName and person.lastName:

```
var person = {

firstName: 'Guybrush',

lastName: 'Threepwood',

get fullName() {
return this.firstName + " " + this.lastName;
},

set fullName(name) {
var parts = name.split(" ");
this.firstName = parts[0];
this.lastName = parts[1];
}

};
```…

Auto-destruct in 41 days

Geordi 2.1.0 released

We released two new versions of geordi. See the changelog below for more details.

Note: Geordi 2.0.0 has a breaking change that affects the geordi commit command.

2.1.0 2019-02-25

Compatible changes

  • Fixes [#59]: Removedb name prefix when reading whitelist
  • Fixes [#62]: Provide better error messages on whitelist editing errors.
  • Fixes [#63]: Allow explicit whitelisting of database names that would be considered derivative during db cleanup
  • Fixes [#64]: Remove VISUAL and EDITOR from …
Repeats

Carrierwave: always limit images to a reasonable size

Today's cameras create huge images, some beyond 50MB. Unless you need to offer this large files, you should always shrink uploaded files to a reasonable resolution.

class ImageUploader < CarrierWave::Uploader::Base
  
  process resize_to_limit: [3000, 3000]
  
  # ...

end
Repeats

Carrierwave processing facts

  1. Class-level process definitions are only applied to the original file
  2. Versions are generated based on the processed original file
  3. Callbacks (before/after) are applied to original file and each version by itself
  4. Under the hood, a version is an instance of the uploader class that has no versions
  5. Version uploader and original uploader can be distinguished by checking #version_name: version uploaders return the version name, whereas the original uploader instance returns nil
  6. Version instances do not have a re…
Repeats

How to organize monkey patches in Ruby on Rails projects

As your Rails project grows, you will accumulate a number of small patches. These will usually fix a bug in a gem, or add a method to core classes.

Instead of putting many files into config/initializers, I recommend to group them by gem in lib/ext:

```text
lib/
ext/
factory_girl/
mixin.rb
carrierwave/
change_storage.rb
fix_cache_ids.rb
sanitize_filename_characters.rb
ruby/
range/
covers_range.rb
array/
dump_to_excel.rb
xss_aware_join.rb
enumerable/

Repeats

How to iterate over an Enumerable, returning the first truthy result of a block ("map-find")

Ruby has Enumerable.find(&block), which returns the first item in the collection for which the block evaluates to true.

first_post_with_image = posts.find do |post|
  post.image
end

However, sometimes it's not the item you're interested in, but some value depening on it – e.g. the value the block evaluated to. You could first map the collection and then take the first truthy value, but this way you need to process the whole collection twice:

first_image_url = posts.map(&:image).find(&:present?).url

If the mapping …

Repeats

Simple database lock for MySQL

Note: For PostgreSQL you should use an alternative that doesn't require a database table. For MySQL we still recommend the solution in this card.


If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.

The attached code provides a database-based mutex for MySQL. You use it by simply calling

Lock....
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