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...

You can not use the hash_including argument matcher with a nested hash:

describe 'user' do
  let(:user) { {id: 1, name: 'Foo', thread: {id: 1, title: 'Bar'} }

  it do 
    expect(user).to match(
      hash_including(
        id: 1, thread: {id: 1}
      )
    )
  end
end  

The example will fail and returns a not very helpful error message:

expected {:id => 1, :name => "Foo", :thread => {:id => 1, :title => "Bar"}} to...

I figure we needed a definitive reference for what work is triggered by changing various CSS properties. It's something I get asked about often enough by developers, and while we can do tests with DevTools, I have both the time and inclination to shortcut that for everyone. I'm nice like that. —Paul Lewis

ActiveRecord::RecordNotFound errors provide quite meaningful error messages that can provide some insight on application details. Consider the following:

ActiveRecord::RecordNotFound: Couldn't find Organisation::Membership with 'id'=12 [WHERE "organisation_memberships"."user_id" = 1]

You should probably not simply render those error messages to the user directly. Instead you you might want to re-raise your own errors. ActiveRecord::RecordNotFound provides you with methods :model and :id where you can get information about w...

Rails 5 (don't know about the others) comes with an initializer wrap_parameters.rb. Here you can tell rails to wrap parameters send to your controllers for specific formats into a root node which it guesses from the controller name.

ActiveSupport.on_load(:action_controller) do
  wrap_parameters format: [:json]
end

This would wrap a flat json body, like

{"name": "Konata"}

that gets send to your UsersController into

{"name" => "Konata", "user" => {"name" => "Konata"}}

Note that the params are now duplicat...

When using geordi for integration tests you might get the following error when trying to run geordi cucumber:

unable to obtain stable firefox connection in 60 seconds (127.0.0.1:7055) (Selenium::WebDriver::Error::WebDriverError)

This means, that the vnc window the tests is talking to has no proper firefox version running. To figure out the issue this might help you:

• Check if the .firefox-version (e.g. 24.0) is the same as ~/bin/firefoxes/24.0/firefox says in the browser
• Maybe [rest...

If your Snom 300 always keeps the same volume for headset and ringtone (as soon as you change one you also change the other), here's what to do:

Go to your phone settings web interface, then Preferences (German Präferenzen). There is the seemingly harmless setting for Ringer Device from Headset (German Klingeltonausgabe bei Kopfhörer). Choose one: "Headset" or "Speaker". Do not select both, otherwise the ringtone volume will always be the same as the headset speaker volume!

You can configure a Ubuntu system as a gateway in order to share it's internet connection (maybe via WLAN or tethering) with other computers on the network.

On the gateway

• Enable ip traffic forwarding:

  • Open /etc/sysctl.conf

  • Uncomment the line

    net.ipv4.ip_forward=1
    

  • Reload using sudo sysctl -p /etc/sysctl.conf

• Reconfigure ip_tables to allow NAT:
  • Download the attached file
  • Replace online_device with the name of the network device that provides the internet connection
    ...

select2 is a great jQuery library to make (large) <select> fields more usable.

For Bootstrap 3 there is select2-bootstrap-theme.
It won't work for Bootstrap 4, but rchavik's fork does (at least with Bootstrap 4 Alpha 6, current version at time of writing this).

It is based on a solution by angel-vladov and adds a few fixes.

Use it by addi...

Capistrano has the concept of a "rollback" that comes in really handy in case of errors. When you notice that your recent deploy was faulty, run cap deploy:rollback and you're back with the previous release. In case of an error during a deployment, Capistrano will rollback itself.

But, you may ask, how can it know how to revert all the custom stuff I'm doing during deployment? It can't. But you can tell it how to.

Capistrano 3

Deploy and rollback are nearly identi...