About the HTML and the BODY tag
The <html> and <body> tags both come with some non-default behavior that you know from other tags.
Do not try to style html or body for positioning, width/heigth, or similar. Every browser has its own caveats and you can not test them all.
Generally speaking:
- Use the
htmltag to define your page's default background color (because on short pages or large screens, yourbodymay not be as tall as the browser window). - Use the
htmltag to define a basefont-sizeso you can use [remunits](https://www.sitepoint.com/underst...
Ubuntu MATE: Add a new panel
To add a new panel in MATE:
- Right-click on an existing panel and choose New Panel
- A new panel will appear at the bottom of the screen
- Right-click on the new panel, choose Properties and uncheck Expand
- Alt+Drag the panel to the desired location (e.g. to a second monitor)
- In the properties, check Expand again.
Using Google Analytics with Unpoly
The default Google Analytics might not work as expected with your Unpoly app. This is because your app only has a single page load when the user begins her session. After that only fragments are updated and the <script> tag that sends the page view to Google Analytics is probably never evaluated again.
Luckily you can fix this.
Simple mode: You just want to track all the page views
Embed your Google Analytics code as always.
Now add the following code snippet:...
There is no real performance difference between "def" and "define_method"
You can define methods using def or define_method. In the real world, there is no performance difference.
define_method is most often used in metaprogramming, like so:
define_method :"#{attribute_name}_for_realsies?" do
do_things
end
Methods defined via define_method are usually believed to have worse performance than those defined via def.
Hence, developers sometimes prefer using class_eval to define methods using def, like this:
class_eval "def #{attribute_name}_for_realsies?; do_things; end"
You can be...
ActiveRecord subselects - Today I Learned
Apparently you can pash a second scope to a hash-condition and the whole thing will be evaluated as a second SELECT statement with a subselect.
Note that sub-queries are extremely slow in MySQL, but they can make cases easier where performance does not matter so much (e.g. a migration on 50K records).
Images darken when getting converted with ImageMagick
When using ImageMagick to manipulate images, you might see that images get darker when beeing modified by newer versions of ImageMagick.
This usually happens with CMYK images beeing converted to RGB by IM.
Solution
At least in our version of ImageMagick (6.7.7) you can solve this by passing this parameter to ImageMagick -colorspace sRGB.
The RGB colorspace was okay for ImageMagick until version 6.6.9. RGB and sRGB switched obviously.
The Codeless Code
The Codeless Code is a charming series of stories about monks and nuns at a programming monastery.
Some stories to get started:
has_one association may silently drop associated record when it is invalid
This is quite an edge case, and appears like a bug in Rails (4.2.6) to me.
Update: This is now documented on Edgeguides Ruby on Rails:
If you set the :validate option to true, then associated objects will be validated whenever you save this object. By default, this is false: associated objects will not be validated when this object is saved.
Setup
# post.rb
class Post < ActiveRecord::Base
has_one :attachment
end
# attachm...
Ruby's default encodings can be unexpected
Note: This applies to plain Ruby scripts, Rails does not have this issue.
When you work with Ruby strings, those strings will get some default encoding, depending on how they are created. Most strings get the encoding Encoding.default_internal or UTF-8, if no encoding is set. This is the default and just fine.
However, some strings will instead get Encoding.default_external, notably
- the string inside a
StringIO.new - some strings created via
CSV - files read from disk
- strings read from an IRB
Encoding.default_external d...
Ruby 2.3 new features
Ruby 2.3.0 has been around since end of 2015. It brings some pretty nice new features! Make sure to read the linked post with its many examples!
Hash#fetch_values
Similar to Hash#fetch, but for multiple values. Raises KeyError when a key is missing.
attrs = User.last.attributes
attrs.fetch_values :name, :email
Hash#to_proc
Turns a Hash into a Proc that returns the corresponding value when called with a key. May be useful with enumerators like #map:
attrs.to_proc.call(:name)
attrs.keys.grep(/name/).map &attrs...
Download Ruby gems without installing
You can download .gem files using gem fetch:
gem fetch activesupport consul
This will produce files like active-support-5.0.0.gem and consul-0.12.1.gem in your working directory.
Dependencies will not be downloaded.
Ruby 2.3.0 has a safe navigation operator
As announced before, Ruby has introduced a safe navigation operator with version 2.3.0. receiver&.method prevents NoMethodErrors by intercepting method invocations on nil.
user = User.last
user&.name # => "Dominik"
# When there is no user, i.e. user is nil:
user&.name # => nil
This might remind you of andand, and indeed it behaves very similar. The only difference is in handling of `fa...
Linux: Find out which processes are swapped out
Processes in Linux might be put into Swap ("virtual memory") occasionally.
Even parts of a single process might be removed from memory and put into Swap.
In order to find out which processes remain within Swap, run this:
sudo grep VmSwap /proc/*/status | egrep -v "0 kB"
Keep in mind Swap is not evil by definition. Some bytes per process beeing put to Swap will not have that much of performance influence.
If you want the Linux virtual memory manager (which is responsible for the decision if and which processes are moved to Swap) to be...
virsh reload xml config file
If you have made any changes to a libvirt xml config file you have to reload is. One way is to reload the whole libvirtd service. But you can just reload corresponding domain xml too:
$ virsh define foo.xml
Ruby 2.3 brings Array#dig and Hash#dig
#dig lets you easily traverse nested hashes, arrays, or even a mix of them. It returns nil if any intermediate value is missing.
x = {
foo: {
bar: [ 'a', { baz: 'x' } ]
}
}
x.dig(:foo, :bar) # => [ 'a', { baz: 'x' } ]
x.dig(:foo, :bar, 1, :baz) # => "x"
x.dig(:foo, :wronk, 1, :baz) # => nil
There is a tiny gem that backports this.
Hack of the day: One-liner to run all Cucumber features matching a given string
The following will search for all .feature files containing a search term and run them using geordi.
find features/ -name '*.feature' | xargs grep -li 'YOUR SEARCH TERM' | sort -u | tr '\n' ' ' | xargs geordi cucumber
If you do not use Geordi, xargs cucumber or similar might work for you.
For details about each command, see [explainshell.com](http://explainshell.com/explain?cmd=find+features%2F+-name+%27*.feature%27+%7C+xargs+grep+-li+%27YOUR+SEARCH+TERM%27+%7C+sort+-u+%7C+tr+%27%5Cn%27+%2...
object-fit polyfill by lazysizes
All new browsers support the new object-fit CSS property. It allows to specify how an element behaves within its parent element and is intended for images and videos. The most useful values are contain (fit-in) and cover (crop).
Unfortunately, IE does not support this yet. However, if you're already using lazysizes, you can use its object-fit polyfill!
Usage
In your Javascript manifest, require them like this:
#= require plugins/object-fit/ls.obj...
request_store: Per-request global storage for your Rails app
Ever needed to use a global variable in Rails? Ugh, that's the worst. If you need global state, you've probably reached for
Thread.current.
When you're using Thread.current, you must make sure you're cleaning up after yourself. Else, values stored in one request may be available to the next (depending on your server). request_store wipes all data when a request ends and makes per-request global storage a no-brainer. Internally, it's using Thread.current with a Hash in a simple middleware.
Example: Remembering all currently a...
Web font rendering on Macs
Macs render fonts bolder than they are, especially on dark background. This can be fixed by configuring the font smoothing:
body
-webkit-font-smoothing: antialiased
-moz-osx-font-smoothing: grayscale
You should do this on every project, all the time.
Stubbing terminal user input in RSpec
Reading user input in console applications is usually done using Kernel#gets. Stubbing that can be a bit hairy.
When your code expects user input, you can not say Kernel.stub(gets: 'user input'). This will have no effect because of reasons.
Instead, you need to know which class will call gets. For example:
described_class.any_instance.stub(gets: 'user input')
If you do not know where gets is called, you can try something like this:
Object.any_instance.stub(gets: 'user input')
Any instance of an object should...
Testing terminal output with RSpec
When testing Ruby code that prints something to the terminal, you can test that output.
Since RSpec 3.0 there is a very convenient way to do that.
Anything that writes to stdout (like puts or print) can be captured like this:
expect { something }.to output("hello\n").to_stdout
Testing stderr works in a similar fashion:
expect { something }.to output("something went wrogn\n").to_stderr
Hint: Use heredoc to test multi-line output.
expect { something }.to output(<<-MESSAGE.strip_heredoc).to_stdout...
HAML 4+ expands nested element attributes
As you may know, HAML expands data attributes that are given as a hash:
%div{ data: { count: 3 } }
# results in:
<div data-count="3"></div>
However, this also works for any other hash attribute. Consider an Angular directive or an Unpoly compiler that is configured by several attributes. Usually you'd prefix them with the directive/compiler name so it gets clear where the attribute belongs. With HAML, this is easy to build:
%...