All our projects have enum-like requirements like this:

• An attribute value must be included in a given set of values.
• The list of allowed values must be retrievable in order to render <select> boxes.
• Each value has a humanized label.
• Sometimes there is a default value.

Most of the time, this requirement is also needed:

• The list of assignable values depends on the user who is currently signed in.

In our past projects there are many different solutions for these related requirements, e.g. ChoiceTrait, methods like `available_...

With different time zones

When dealing with time zones in Rails, there is one key fact to keep in mind:

Rails has configurable time zones, while
Ruby is always in the server's time zone

Thus, using Ruby's time API will give you wrong results for different time zones.

For consistency, you should only use Rails' methods, but the hard thing is to know which method originates from Ruby and which from Rails. To simplify this, adhere to the following suggestion:

Use Time.zone for everything time-related

# Examp...

Rails' ActiveSupport::TimeWithZone objects have both a timezone code and offset, e.g. Thu, 28 Mar 2019 16:00:00 CET +01:00. Ruby's stdlib TZInfo also has time zones, but with different identifiers.
Unfortunately, not all timezone codes can be used to parse strings or to move time objects into another time zone.

Some timezone codes like CET are supported by ActiveSupport extensions like String#in_time_zone, while many codes will actually not work:

>> '2019-03-01 12:00'.in_time_zone('PST')
ArgumentError (Invalid Timezone: PST)
...

When you need to insert many records into the same table, a fast way to do it is to have a single INSERT statement describing multiple rows. Unfortunately there is no way to do this through ActiveRecord.

What you can do to save time is to open a transaction and save multiple records within that transaction:

transaction do
  500.times { Model.create! }
end

Although you will still trigger 500 INSERT statements, they will complete considerably faster.

When I trie...

Fixed bugs where calling valid? would change the record's state.

When you have a powerful machine with many CPU cores, you might run into an error like

ERR DB index is out of range (Redis::CommandError)

This is because Redis defaults to at most 16 databases (0 to 15) and running tests in parallel might exceed that (your tests might run on databases 1..n or 2..(n+1)).

You can increase that limit:

1. Get number of CPUs of your machine.

   nproc --all
   

2. Open up Redis configuration file.

   sudo vim /etc/redis/redis.conf
   

3. Find databases row and increase it, e.g. set to CPU cou...

We tend to use database transactions as a magic bullet to get rid of all our concurrency problems. When things get really bad, we might even throw in some locking mechanism, but then are usually done with it.

Unfortunately, transactions semantics in databases are actually very complicated, and chances are, your making some incorrect assumptions.

The MySQL innodb engine actually has [four different modes](ht...

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...

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...

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' 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.

# 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...

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];
  }

};
```...

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...

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....