Trying to open a vnc window with geordi geordi vnc ended up with this error:

> VNC viewer could not be opened:
vncviewer: ConnectToTcpAddr: connect: Connection refused

Check if vncserver 17 (default geordi session) is running:

ps -aux|grep vnc

If you see Xvnc4 :17 then the server is already running. Kill this server if it is already running.

vncserver -kill :17

Als...

mysql> SELECT @@global.version;
+------------------+
| @@global.version |
+------------------+
| 5.6.30           |
+------------------+
1 row in set (0,00 sec)

MySQL 5.6 Reference Manual says "BLOB and TEXT columns cannot have DEFAULT values".

If you want to run migrations in development here are two variants which might help. If you are not sure about the side effects (e.g. your application is broken when it doesn't set additional default values on application side, too...

If you want to make a screenshot of a website that works well in print or on a high-DPI screen (like Apple Retina displays), here is how you can capture a high-resolution screenshot.

You can do this without an addon:

• Open the website
• If you have multiple monitoros:
  • Resize the Chrome window so it covers multiple monitors (in Linux you can hold ALT and resize by dragging with the right mouse button)
  • Zoom into the page using CTRL + and CTRL - so it covers most of the window area. Leave a little padding on the left and right so...

About-Payments is here to help you to accept payments online and
find the best payment service provider for your e-commerce business.

TL;DR Use user.update!(remove_avatar: true) to delete attachments outside of forms. This will have the same behavior as if you were in a form.

As you know, Carrierwave file attachments work by mounting an Uploader class to an attribute of the model. Though the database field holds the file name as string, calling the attribute will always return the uploader, no matter if a file is attached or not. (Side note: use #present? on the uploader to check if the file exists.)

class User < ApplicationRecord
  mount :avatar, ...

This is painful. Consider using Microsoft Office or switching careers. If you need to write < 20 letters consider doing it manually.

So you didn't listen and here it comes:

1. Ignore the Mail Merge Wizard. It will crash or destroy your document.
2. Export your addresses, recipient names, etc. as a .ods spreadsheet (.xls, .xlsx, .ods). Use any columns that work for you, but be consistent. I like to use one column for the address, one column for the salutation line.
3. Import the spreadsheet as an address book source: *Tools => Add...

When making requests using curl, no cookies are sent or stored by default.
However, you can tell curl to re-use cookies received earlier (or forge your own cookies).

There are 2 command line switches you need to use:

• -c will write cookies to a given file
• -b will read cookies from a given file

Example

The remote server sets a "foo" cookie to value "bar". We tell curl to store them to a file at /tmp/cookies using the -c switch.

$ curl -c /tmp/cookies http://httpbin.org/cookies/set?foo=bar

You may look at the file, ...

You should avoid using application models in your migrations. But how else could you create records in a migration?

The most basic way is to write plain SQL, but since INSERT statements are no pleasant write for Rubyists, here is a simple wrapper:

Record creation helper for migrations

The helper method below takes a table name and a hash of attributes, which it inserts into the specified table. Copy it over to your migration and profit!

  private

  def insert_record(table, **attributes)
    attributes.merge!...

When you print (or print preview) and elements are cut off (e.g. after 1st page, or "randomly") you should check your CSS rules for these:

• Is there an element with "display: inline-block" that surrounds your content? Make sure it has "display: block" for printing.
  This primarily affects Firefox and Internet Explorer. Chrome seems to be able to handle inline-block elements in most cases.

• Does the element itself, or a container, define "overflow: hidden"? Use "overflow: auto" (or maybe "overflow: visible") instead.

• Is th...

By default, browsers will not wrap text at syllable boundaries. Text is wrapped at word boundaries only.

This card explains some options to make browsers wrap inside a long word like "Donaudampfschifffahrt".

Option 1: hyphens CSS property (preferred)

Modern browsers can hyphenate natively. Use the hyphens CSS property:

hyphens: auto

There is also hyphens: none (disable hyphenations even at ­ entities) and hyphens: manual (hy...

Summary: Don't add chromedriver-helper to the Gemfile

• the executables might break your tests in projects where chromedriver-helper is not in the Gemfile
• developers with different chrome versions will have problems using the same chromedriver-helper version

Background

If you install the chromedriver-helper gem, but don't have it in you Gemfile, your selenium tests might fail with:

Selenium::WebDriver::Error::WebDriverError: unable to connect to chromedriver 127.0.0.1:9515

The reason is that chromedriver-helper ov...

We're usually running Ubuntu LTS versions. Sometimes newer hardware requires packages from more recent Ubuntu releases that only come with 6 months of support. If there is really no other way, it's possible to install packages from later Ubuntu releases

Caution: Pay really close attention to what you're doing. Depending on the package, this process may require upgrading a lot of dependencies, possibly breaking the system! You really should not do this unless you've carefully calculated the impact on your system

Preparation

First,...

Checking if a JavaScript value is of a given type can be very confusing:

• There are two operators typeof and instanceof which work very differently.
• JavaScript has some primitive types, like string literals, that are not objects (as opposed to Ruby, where every value is an object).
• Some values are sometimes a primitive value (e.g. "foo") and sometimes an object (new String("foo")) and each form requires different checks
• There are three different types for null (null, undefined and NaN) and each has different rules for...

An end-to-end test (E2E test) is a script that remote-controls a web browser with tools like Selenium WebDriver. This card shows basic techniques for fixing a flaky E2E test suite that sometimes passes and sometimes fails.

Although many examples in this card use Ruby, Cucumber and Selenium, the techniques are applicable to all languages and testing tools.

Why tests are flaky

Your tests probably look like this:

When I click on A
And I click on B
And I click on C
Then I should see effects of C

A test like this works fine...

When your public-facing application has a longer downtime for server maintenance or long migrations, it's nice to setup a maintenance page to inform your users.

When delivering the maintenance page, be very careful to send the correct HTTP status code. Sending the wrong status code might get you kicked out of Google, or undo years of SEO work.

Popular footguns

Here are some ways to shoot yourself in the foot during maintenance:

• If all your routes send a "200 OK" with a HTML body "We're b...

Slides for Henning's talk on Sep 21st 2017.

Understanding sync vs. async control flow

Talking to synchronous (or "blocking") API

print('script start')
html = get('/foo')
print(html)
print('script end')

Script outputs 'script start', (long delay), '<html>...</html>', 'script end'.

Talking to asynchronous (or "evented") API

print('script start')
get('foo', done: function(html) {
  print(html)
})
print('script end')

Script outputs 'script start', 'script end', (long ...

If you are using PDFKit / wkhtmltopdf, you might as well want to use custom fonts in your stylesheets. Usually this should not be a problem, but at times they include misleading Meta-information that leads to a strange error in the PDF.

The setup

• The designer gave you two fonts named something like BrandonText-Regular and BrandonText-Bold. (With flawed Meta-information)
• You have a HTML string to be rendered by PDFKit
• For demonstration purposes, this strin...

The linked article shows how to exploit websites that include unsanitized user input in their CSS.

Although the article often mentions React and CSS-in-JS libraries, the methods are applicable to any web app that injects user input into style tags or properties.

Also, sanitizing user input for CSS injection is much harder than sanitizing HTML.

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...

When localizing model attributes via I18n you may run into errors like this:

I18n::InvalidPluralizationData: translation data { ... } can not be used with :count => 1. key 'one' is missing.

They seem to appear out of the blue and the error message is more confusing than helpful.

TL;DR A model (e.g. Post) is lacking an attribute (e.g. thread) translation.
Fix it by adding a translation for that model's attribute (attributes.post.thread). The error message reveals the (wrongly) located I18n data (from `attributes.thread...

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...