When your model is using a callback like before_save or before_validation to calculate an aggregated value from its children, it needs to skip those children that are #marked_for_destruction?. Otherwise you will include children that have been ticked for deletion in a nested form.

Wrong way

class Invoice < ApplicationRecord
  has_many :invoice_items
  accepts_nested_attributes_for :invoice_items, :allow_destroy => true # the critical code 1/2
  before_save :calculate_and_store_amount                              # the crit...

Getting an entire test suite green can be a tedious task which involves frequent switches between the CLI that is running tests back to the IDE where its cause can be fixed.

The following bash aliases helped me speed up that process:

alias show-next-failure="bundle exec rspec --next-failure"
alias open-next-failure="show-next-failure || show-next-failure --format json  | jq -r '.examples[0]' | jq '\"--line \" + (.line_number|tostring) + \" \" + .file_path' | xargs echo | xargs rubymine"

There is a lot going on above but the gist...

This Capistrano task runs a command on all servers.

bundle exec cap production app:run cmd='zgrep -P "..." RAILS_ROOT/log/production.log'

Code

# lib/capistrano/tasks/app.rake

namespace :app do

  # Use e.g. to grep logs on all servers:
  #   b cap production app:run_cmd cmd='zgrep -P "..." RAILS_ROOT/log/production.log' 
  #
  # * Use RAILS_ROOT as a placeholder for the remote Rails root directory.
  # * Append ` || test $? =1;` to grep calls in order to avoid exit code 1 (= "nothing found")
  # * To be able to process ...

When projects run for many years, they require special regular maintenance to stay fresh. This kind of maintenance is usually not necessary for small or quick projects, but required to keep long-running projects from getting stale.

You should be able to fit this into a regular development block.

Quarterly

Check which libraries need updating

As time goes by, libraries outdate. Check your software components and decide if any of it needs an update. Your main components (e.g. Ruby, Rails, Unpoly) should always be reasonably up to da...

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...

There is no such thing as a "default order" of rows in database tables.

For instance, when you paginate a result set: When using LIMIT, it is important to use an ORDER BY clause that constrains the result rows into a unique order. Otherwise you will get an unpredictable subset of the query's rows. You might be asking for the tenth through twentieth rows, but tenth through twentieth in what ordering? The ordering is unknown, unless you specified ORDER BY.

In Rails, if you use Record.first or Record.last, it will default to orderin...

In the Gitlab settings the flag Auto-cancel redundant pipelines is enabled by default. This auto-cancels jobs that have the interruptible setting set to true (defaults to false e.g. to not cancel deploys by accident).

Consider to set the interruptible flag for test jobs to reduce the load on your runners like in the following example .gitlab-ci.yml:

rubocop:
  interruptible: true
  script:
    - 'bundle exec rubocop'

rspec:
  int...

The need for clearfix hacks has been greatly reduced since we could layout with Flexbox or CSS Grid.

However, when you do need a clearfix, there's no reason to use a hack anymore. You can just give the clearing container display: flow-root.

This is supported by all browsers except IE11.

To return non-HTML responses (like XLS spreadsheets), we usually use the

respond_to do |format|
  format.xls do
    # send spreadsheet
  end
end

This is often, but not always the same as checking for params[:format] == :xls, so don't rely on this when e.g. one format checks for authorization and the other doesn't.

params[:format] is only set when a user explicitly puts a .xls at the end of the URL.

The format.xls block also responds when the user's browser requests the application/excel MIME type.

If Internet Explo...

A great two-part article about various hacks you can use to create great-looking screen designers when you're not a designer.

Part 1 contains:

• Light comes from the sky
• Black and white first
• Double your whitespace

Part 2 contains:

• Learn the methods of overlaying text on images
• Make text pop— and un-pop
• Only use good fonts
• Steal like an artist

OpenAI is currently limiting the Audio generating API endpoint to text bodies with a maximum of 4096 characters.
You can work around that limit by splitting the text into smaller fragments and stitch together the resulting mp3 files with a CLI tool like mp3wrap or ffmpeg.

Example Ruby Implementation

Usage

input_text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Mi eget mauris pharetra et ultrices neque."
output_mp3_path = Rails.root.join("tts/ipsum...

In Capistrano 3, your Capfile requires 'capistrano/rails/migrations', which brings two Capistrano tasks: deploy:migrate and deploy:migrating. The former checks whether migrations should be performed. If so, the latter is invoked, which performs the actual migrations.

Knowing this, it is easy to dump the db only if migrations will run. First, enable conditional migrations:

# config/deploy.rb
set :conditionally_migrate, true # Only attempt migration if db/migrate changed

Then hook up the dump task to deploy:migrating:

#pluck is commonly used as a performant way to retain single database values from an ActiveRecord::Relation

Book.pluck(:title, :price) #=> [["The Hobbit", "8.99"], ["The Alchemist", "7.89"]]

But #pluck can do more: you can query multiple tables as well!

Book.joins(:author).pluck("books.title, books.price, authors.name") #=> [["The Hobbit", "8.99", "J. R. R. Tolkien"], ["The Alchemist", "7.89", "Paulo Coelho"]]

Note the use of :author for the joins, and then authors for the pluck clause. The first corresp...

• Added: State machine can now use the :prefix-option to avoid name collision if you define multiple state machines on the same model, and use state names more than once
  • Previously state_machine-definitions like this:

      class Form
      
        state_machine :first_wizard_stage do
          state :completed
        end
    
        state_machine :second_wizard_stage do
          state :completed
        end
        
      end
    

    would produce the following warning:

      rails_state_machine-2.1....
    

Getting CSS (and JS) live reloading to work in a esbuild / Rails project is a bit of a hassle, but the following seems to work decently well.

We assume that you already use a standard "esbuild in Rails" setup, and have an esbuild watcher running that picks up your source code in app/assets and compiles to public/assets; if not change the paths below accordingly.

Basic idea

We will

• use the guard-livereload gem as the livereload server (which send updates to the browser),
• use the livereload-js npm package in the browser to con...

To keep JavaScript sources small, it can sometimes make sense to split your webpack bundles. For example, if your website uses some large JavaScript library – say TinyMCE – which is only required on some selected pages, it makes sense to only load that library when necessary.

In modern webpack this is easily doable by using the asynchronous import function.

Say we have an unpoly compiler that sets up TinyMCE like this (code is somewhat simplified):

// TinyMCE as part of the main bundle!

import tinymce from 'tinymce/tinymce'

// U...

In MySQL,

CONCAT('foo', 'bar', NULL) = NULL

the NULL always wins in MySQL.

If you would rather treat NULL as an empty string, use CONCAT_WS (concatenation with separator) instead:

CONCAT_WS('', 'foo', 'bar', NULL) = 'foobar'

PostgreSQL

In PostgreSQL the NULL is not viral in CONCAT:

CONCAT('foo', 'bar', NULL) = 'foobar'

Note: For PostgreSQL you should use advisory locks. 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 model level mutex for MySQL. You use it by simply calling

Lock.acquire('string to synchronize on') do
  # non-th...

Make sure that you use the correct property when editing an HTML attribute. Using innerHTML with unsafe arguments makes your application vulnerable to XSS.

• textContent: Sets the content of a Node (arguments are HTML-safe escaped)
• innerHTML: Sets the HTML of an Element (arguments are not escaped and may not contain user content)

Hierarchy

This hierarchy gives you a better understanding, where the textContent and the innerHTML properties are defined. It also includes (just for completeness) the innerText property, whi...

If you ever need to restore exact records from one database to another, Marshal might come in handy.

Marshal.dump is part of the ruby core and available in all ruby versions without the need to install anything. This serializes complete ruby objects including id, object_id and all internal state.

Marshal.load deserializes a string to an object. A deserialized object cannot be saved to database directly as the the dumped object was not marked dirty, thus rails does not see the need to save it, even if the object is not present in...

tl;dr

You can use ordered to ensure that messages are received in a specific order.

Example

expect(ClassA).to receive(:call_first).ordered
expect(ClassB).to receive(:call_second).ordered
expect(ClassB).to receive(:call_third).ordered

#ordered supports further chaining

Example

When defining a trait using the Modularity gem, you must take extra steps to define constants to avoid caveats (like when defining subclasses through traits).

tl;dr

In traits, always define constants with explicit self.

If your trait defines a constant inside the as_trait block, it will be bound to the trait module, not the class including the trait.
While this may seem unproblematic at first glance, it becomes a problem when including trai...

Event delegation is a pattern where a container element has a single event listener that handles events for all descendants that match a CSS selector.

This pattern was popularized by jQuery that lets you do this:

$('.container').on('click', '.message', function(event) {
  console.log("A message element was clicked!")
})

This technique has some advantages:

1. When you have many descendants, you save time by only registering a single listener.
2. When the descendants are changed dynamic...

Our gem spreewald supports a few helpers for development. In case you notice errors in your Cucumber tests, you might want to use one of them to better understand the underlying background of the failure. The following content is also part of the spreewald's README, but is duplicated to this card to allow repeating.

Then console

Pauses test execution and opens an IRB shell with current cont...