TL;DR: Bundler 2.0 will rename Gemfile to gems.rb and Gemfile.lock to gems.locked (sic).

The old filenames will be supported until the release of Bundler 3.0.

Some more breaking changes here.

You need to set the :inverse_of option manually for relations that have an association to a polymorphic model. Otherwise you will not be able to save a record with a nested polymorphic association.

class Event < ApplicationRecord
  has_many :letters, as: :record
end

class Letter < ApplicationRecord
  belongs_to :record, polymorphic: true
end

event = Event.new.letters.build
event.save! # => ActiveRe...

While the hardware mute button of my Lenovo x230 worked on Ubuntu 14.04 out of the box, it does not on Ubuntu 16.04. It is fairly simple to fix, though.

There is an extensive answer on Ask Ubuntu, but only part of it was required for me. Here is the gist of it.

1. Open a terminal

2. Run acpi_listen and press the mute key. You should see something like this:

   button/f20 F20 00000080 00000000 K
   

   Press Ctrl+C to exit.

3. Run amixer scontrols. You will see multiple lines, one of which sh...

Let's say you have a form that you render a few times but you would like to customize your submit section each time. You can achieve this by rendering your form partial as layout and passing in a block. Your template or partial then serves as the surrounding layout of the block that you pass in. You can then yield back the form to the block and access the form in your block.

-# record/_form.haml

= form_for record do |form|
  -# ...
  .form-actions
    yield(form)
  

In order to make your template record/_form.haml accept a...

FactoryBot allows a :class option to its factory definitions, to set the class to construct. However, this option is not supported for traits.

Most often, you can just define a nested factory instead of a trait, and use the :class option there.

factory :message do
  factory :reply, class: Message::Reply do
    # ...
  end
end

If you need/want to use traits instead (for example, it might make more sense semantically), you can not use a :class on a trait.

In that case, use initialize_with to define the record's constr...

There are several gems that make it easy to read and process xlsx files. Parsing the entire file at once however is error-prone since each cell is transformed to a ruby object - sometimes including thousands of formatted but empty cells.

As of today, I found two promising alternatives that provide a stream-based access to spradsheet rows:

• Roo supports multiple spreadsheet types like ODS or CSV and has a quite large contributor base
• [Creek](https://github.com/pythonicrubyis...

On my Ubuntu MATE machine, switching applications with ALT + TAB was impossible, because it took nearly 2 seconds. The culprit appears to be an "UX improvement" gone bad: MATE renders a live screenshot of each running application inside the application switcher.

Fixing this is simple:

• Open "Window Preferences"
• Either uncheck "Enable software compositing window manager" or check "Disable thumbnails in Alt-Tab"

The linked documentation explains how to get a JSON list of the latest 100 events of a given issue. Simply open this URL while logged in:

https://sentry.io/api/0/issues/<issue id>/events/

If another session is accessing your database you are trying to reset or drop you might have seen the following error:

PG::ObjectInUse: ERROR:  database "foo_development" is being accessed by other users
DETAIL:  There is 1 other session using the database.

This could be the rails server, rubymine and many more. Beside terminating the session connection manually you can also find out the pid and kill the process.

1. rails db
2. SELECT * FROM pg_stat_activity;

datid            | 98359
datname          | foo_developm...

You need to disable "Bluetooth low energy", then follow these core steps:

1. Make sure the headphones are in pairing mode.
2. Pair with System Settings > Bluetooth. On 16.04 I had to choose "proceed without pairing" and enter the PIN "0000"
3. Select & test the headphones in System Settings > Sound. Choose High Fidelity Playback (A2DP Sink).

I also had to install a package with sudo apt-get install pulseaudio-module-bluetooth and load it with pactl load-module module-bluetooth-discover. Put the latter command into ~/.bashrc or you'll...

Here is some JavaScript code that allows you to click the screen and get the clicked element's text contents (or value, in case of inputs).

The approach is simple: we place an overlay so you don't really click the target element. When you click the overlay, we look up the element underneath it and show its text in a browser dialog. You can then copy it from there.

While moving the mouse, the detected element is highlighted.

Here is the one-liner URL that you can store as a bookmark. Place it in your bookmarks bar and click it to activate....

I frequently find myself needing a combination of group_by, count and sort for quick statistics. Here's a method on Enumerable that combines the three:

module Enumerable

  def count_by(&block)
    group_by(&block)
      .transform_values(&:count)
      .sort_by(&:last)
      .to_h
  end
  
end

Just paste that snippet into a Rails console and use #count_by now!

Usage examples

• Number of email addresses by domain:

> User.all.count_by { |user| user.email.sub /^.*@/, '' }
=> { "sina.cn"=>2, ..., "hotmail.co...

Sometimes modern Javascript projects get out of hand. A major culprit in this can be the messy handling of asynchronous tasks, leading to long, complex, and deeply nested blocks of code. Javascript now provides a new syntax for handling these operations, and it can turn even the most convoluted asynchronous operations into concise and highly readable code.

Native promises have no methods to inspect their state.

You can use the promiseState function below to check whether a promise is fulfilled, rejected or still pending:

promiseState(promise, function(state) {
  // `state` now either "pending", "fulfilled" or "rejected"
});

Note that the callback passed to promiseState will be called asynchronously in the next [microtask](https://jakearchibald.com/2015/tasks-microtasks-queues-and-schedules/...

If you want to ssh into your vagrant box without switching into the project directory and typing vagrant ssh, you can also create an entry directly in ~/.ssh/config. This will allow you to use ssh <my-box> from anywhere. Simply paste the information provided by vagrant ssh-config to your ~/.ssh/config-File: vagrant ssh-config >> ~/.ssh/config

Example:

$ vagrant ssh-config
Host foobar-dev
  HostName 127.0.0.1
  User vagrant
  Port 2200
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no
  PasswordAuthentication no
  Id...

As described by the linked Stackoverflow answer, run these commands:

sudo add-apt-repository ppa:git-core/ppa -y
sudo apt-get update
sudo apt-get install git
git --version

This will get you Git 2.6.4 (as of Dec 2015).

Troubleshooting

If you don't have add-apt-repository yet, install it with:

sudo apt-get install python-software-properties software-properties-common

Scope is all about where something is visible. It’s all about what (variables, constants, methods) is available to you at a given moment. If you understand scope well enough, you should be able to point at any line of your Ruby program and tell which variables are available in that context, and more importantly, which ones are not.

The article gives detailed explanation on the variable scope in ruby with examples that are easy to understand. Every ruby developer should at least know the first part of the article by heart. The second half ...

rack-cargo gives your API a new /batch route that lets clients perform multiple API calls with a single request.

The batched calls are resolved internally and are then returned as an array of responses:

// This is batch request payload:
{
    "requests": [
        {
            "name": "order",
            "path": "/orders",
            "method": "POST",
            "body": {
                "address": "Home, 12345"
            }
        },
        {
            "name": "order_item",
...

Use Traim to build a RESTful API for your ActiveRecord models with very little code.

Traim assumes your API resources will map 1:1 to your ActiveRecord models and database tables. This assumption usually falls apart after a few months into a project, so be ready to replace your Traim API with something more expressive afterwards.

Traim outputs a Rack application which you can either serve standalone or mount into your Rails app.

Sometimes you add Paperclip image styles, sometimes you remove some. In order to only keep the files you actually need, you should remove stale Paperclip styles from your server.

This script has been used in production successfully. Use at your own risk.

# Config #######################################################################
delete_styles = [:gallery, :thumbnail, :whatever]
scope = YourModel # A scope on the class with #has_attached_file
attachment_name = :image # First argument of #has_attached_file
noop ...

Re-creating a complex ActiveRecord scenario quickly without setting up a full-blown Rails app can come in handy e.g. when trying to replicate a presumed bug in ActiveRecord with a small script.

# Based on http://www.jonathanleighton.com/articles/2011/awesome-active-record-bug-reports/ 

# Run this script with `$ ruby my_script.rb`
require 'sqlite3'
require 'active_record'

# Use `binding.pry` anywhere in this script for easy debugging
require 'pry'

# Connect to an in-memory sqlite3 database
ActiveRecord::Base.establish_connection(
  ad...

In the ruby shell (IRB) and rails console the return value of the previous command is saved in _ (underscore). This might come in handy if you forgot to save the value to a variable and further want to use it.

Example:

irb(main):001:0> 1 + 2
=> 3
irb(main):002:0> _
=> 3
irb(main):003:0> a = _
=> 3

Auto-cropping

ImageMagick can automatically crop surrounding transparent pixels from an image:

convert input.png -trim +repage output.png

You need to +repage to update the image's canvas, or applications will be randomly confused.
Trimming specific colors is also possible, see the documentation.

Resizing into a box

Occasionally, you want to resize an image to a maximum width or height, and change the "outer" image dimensions to something that won't match the input image.

To re...