Controlling how your website appears on social media feeds
When a user shares your content, a snippet with title, image, link and description appears in her timeline. By default social networks will use the window title, the first image, the current URL and some random text snippet for this purpose. This is often not what you want.
Luckily Facebook, Twitter, etc. lets you control how your content appears in the activity streams. They even have agreed on a common format to do this: OpenGraph <meta> tags that go into your HTML's <head>:
<meta property="og:url" content="http://start.makan...
Dealing with I18n::InvalidPluralizationData errors
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)….
Regex: Be careful when trying to match the start and/or end of a text
Ruby has two different ways to match the start and the end of a text:
^(Start of line) and$(End of line)\A(Start of string) and\z(End of string)
Most often you want to use \A and \z.
Here is a short example in which we want to validate the content type of a file attachment. Normally we would not expect content_type_1 to be a valid content type with the used regular expression image\/(jpeg|png). But as ^ and $ will match lines, it matches both content_type_1 and content_type_2. Using \A and \z will wo…
Write custom RSpec matchers
There are three ways to define your own RSpec matchers, with increasing complexibility and options:
1) Use RSpec::Matchers.define
RSpec::Matchers.define :be_a_multiple_of do |expected|
match do |actual|
actual % expected == 0
end
# optional
failure_message do |actual|
"expected that #{actual} would be a multiple of #{expected}"
end
# optional
failure_message_when_negated do |actual|
"expected that #{actual} would not be a multiple of #{expected}"
end
end
This is automat…
Matching unicode characters in a Ruby (1.9+) regexp
On Ruby 1.9+, standard ruby character classes like \w, \d will only match 7-Bit ASCII characters:
"foo" =~ /\w+/ # matches "foo"
"füü" =~ /\w+/ # matches "f", ü is not 7-Bit ASCII
There is a collection of character classes that will match unicode characters. From the documentation:
/[[:alnum:]]/Alphabetic and numeric character/[[:alpha:]]/Alphabetic character/[[:blank:]]/Space or tab/[[:cntrl:]]/Control character/[[:digit:]]/Digit/[[:graph:]]/Non-blank character (excludes spaces, co…
RubyMine users: you should be using bookmarks
RubyMine allows bookmarking lines of code. This is super-helpful when working on a complex problem.
I've been using this feature for a few years now, and so should you! :)
Here are the default Linux/Windows keystrokes. See the documentation for other keybindings.
Add an anonymous bookmark
F11
A gray checkmark will be shown in the gutter on the left.
If you press F11 again on a bookmarked line, the bookmark will be removed.
Add a named bookmark ("mnemonic")
Ctrl …
When upgrading/downgrading RubyGems and Bundler on a server, you must clear bundled gems
On application servers, gems are usually bundled into the project directory, at a location shared across deployments.
This is usually shared/bundle inside your project's root directory, e.g. /var/www/your-project/shared/bundle/.
If you can't find that, take a look at current/.bundle/config and look for BUNDLE_PATH.
When you are changing the version of RubyGems or Bundler on a system where gems are installed this way, you must wipe that bundle directory in addition to the user and system gems or gems that are already ins…
Be very careful with 301 redirects
Browsers support two kinds of redirects:
301 moved permanently302 moved temporarily
Be very careful with the 301 type. Most browsers seem to cache these redirects forever, unless you set different Cache-Control headers. If you don't have any cache control headers, you can never change them without forcing users to empty their cache.
The only fix is to keep redirecting the user to the correct page, so if you had
/page-1 --301--> /page-2
but you want
/page-1 --301-> /page-3
your only fix is to change it to
…
Ruby: How to use global variables for a conditional debugger
You can share a state in Ruby with global variables. Even if you should avoid them whenever possible, for debugging an application this could be temporary quite handy.
Example:
class User
after_save { byebug if $debug; nil }
def lock
self.locked = true
save
end
end
```
Rspec.describe User do
let(:user) { create(:user) }
before do
# Many users are created and saved in this hook, but we don't want the debugger to stop for them
end
…
Unpoly: Automatically show the full better_errors page when Rails raises an error
When an AJAX request raises an exception on the server, Rails will show a minimal error page with only basic information. Because all Unpoly updates work using AJAX requests, you won't get the more detailled better_errors page with the interactive REPL.
Below is an event listener that automatically repeats the request as a full-page load if your development error shows an error page. This means you get…
Use Time.current / Date.current / DateTime.current on projects that have a time zone
Basically, you now need to know if your project uses a "real" time zone or :local, and if config.active_record.time_zone_aware_attributes is set to false or not.
-
With time zones configured, always use
.currentforTime,Date, andDateTime.ActiveRecord attributes will be time-zoned, and
.currentvalues will be converted properly when written to the database.
Do not useTime.nowand friends. Timezone-less objects will not be converted properly when written to the database. -
With no/local time zone use
Time.now, `…
CSS: Don't target multiple vendor-prefixed pseudo-elements in a single rule
Some pseudo-elements need to be addressed with vendor prefixes. E.g. ::selection is not supported by Firefox, you need to use ::-moz-selection instead.
What you cannot do is to define a single CSS rule to address both the standard and vendor-prefixed form:
::selection, ::-moz-selection {
background-color: red;
}
This rule will be ignored by all browsers. The reason is that if a browser doe…
Project management best practices: Working with clients in person
When working on a bigger project, the easiest way to improve your work relation with a client or an external product manager, is to make sure you see them in person once in a while.
It makes sense to meet each other when you start working together to establish a relationship and find out what makes them tick.
If you need to discuss a larger package of work, use the opportunity and meet up and discuss it in person.
When you have to discuss something in your daily work, prefer talking to writing, and consider using a webcam.
CSS font metrics in detail
Line-height and vertical-align are simple CSS properties. So simple that most of us are convinced to fully understand how they work and how to use them. But it’s not. They really are complex, maybe the hardest ones, as they have a major role in the creation of one of the less-known feature of CSS: inline formatting context.
For example, line-height can be set as a length or a unitless value 1, but the default is normal. OK, but what normal is? We often read that it is (or should be) 1, or maybe 1.2, even the CSS spec is unclear on that…
Choosing the right gems for your project
Adding a gem means you take over the liability towards the external code.
Checklist
Based on "To gem, or not to gem":
- Gem is really needed (prefer writing your own code for simple requirements without many edge cases)
- Gem is tested well (coverage and quality)
- Gem has a good code quality
- Gem's licence fits to the project requirement
- Try to avoid gems that do much more than your requireme…