Thread-safe collections in Ruby
When using threads, you must make your code thread-safe. This can be done by either locking (mutexes) all data shared between threads, or by only using immutable data structures. Ruby core classes like String or Array are not immutable.
There's several gems providing thread-safe collection classes in Ruby.
concurrent-ruby
The concurrent-ruby gem provides thread-safe versions of Array and Hash:
```
sa = Concurrent::Array.new # supports standard Array.new forms
sh = Conc…
RSpec: How to define classes for specs
RSpec allows defining methods inside describe/context blocks which will only exist inside them.
However, classes (or any constants, for that matter) will not be affected by this. If you define them in your specs, they will exist globally. This is because of how RSpec works (short story: instance_eval).
describe Notifier do
class TestRecord
# ...
end
let(:record) { TestRecord.new }
it { ... }
end
# TestRecord will exist here, outside of the spec!
This will come bite you at least when you try to define a clas…
How to: Use git bisect to find bugs and regressions
Git allows you to do a binary search across commits to hunt down the commit that introduced a bug.
Given you are currently on your branch's HEAD that is not working as expected, an example workflow could be:
git bisect start # Start bisecting
git bisect bad # Tag the revision you are currently on (HEAD) as bad. You could also pass a commit's SHA1 like below:
git bisect good abcdef12345678 # Give the SHA1 of any commit that was working as it should
# shorthand:
git bisect start <bad ref> <good ref>
Git will fetch a comm…
Hiding the clear input button of Edge (with EdgeHTML engine)
Edge (and some versions of Internet Explorer, like IE11) use to render a × clear input button on text fields. While this is intended as a nicety for users, it comes in annoying when you've built and styled your own clear input button.
Hide the Edge × with this pseudo selector:
input::-ms-clear
display: none
IE11 ignores calc() functions in the flex shorthand
Example (broken in IE):
flex: 0 1 calc(50% - 20px)
Workaround:
flex-basis: calc(50% - 20px)
flex-grow: 0 // Default, can be omitted for this example
flex-shrink: 1 // Default, can be omitted for this example
The Difference Between Width and Flex Basis | Geddski
Within a Flexbox layout, there are multiple CSS attributes that may affect a child's basis (the initial width before flexing). You might be confused how flex-basis, width, min-width and the intrinsic width of your content play together.
The attached article explains the differences. In summary:
- If a
flex-basisis set, that is used as the basis - If no
flex-basisis set, thewidthis used as the basis - If neither
flex-basisnorwidthis set, the content…
Faking and testing the network with WebMock
An alternative to this technique is using VCR. VCR allows you to record and replay real HTTP responses, saving you the effort to stub out request/response cycles in close details. If your tests do require close inspection of requests and responses, Webmock is still the way.
WebMock is an alternative to FakeWeb when testing code that uses the network. You sh…
Google Analytics: Change the tracked URL path
By default, Google Analytics tracks the current URL for every request. Sometimes you will want to track another URL instead, for example:
- When an application URL contains a secret (e.g. an access token)
- When you want to track multiple URLs under the same bucket
- When you want to track interactions that don't have a corresponding URL + request (e.g. a Javascript button or a PDF download)
Luckily the Analytics code snippet allows you to freely choose what path is being tracked. Simple change this:
ga('send', 'pageview');
… to th…
Rails: Do not load frameworks you don't need
Rails is split into a large number of (sub-) frameworks.
The most important and central of those are
- activesupport (extends the Ruby standard library)
- activerecord / activemodel (ORM for Rails)
- actionview / actionpack (controller / views)
- actionmailer (sends mails)
However, there are also some more situational frameworks included, such as
- actioncable (real time communications using websockets)
- actionmailbox (receives mails)
- actiontext (support for WYSIWYG text editor)
- activejob (background jobs)
- activestorage (file uplo…
Cucumber pitfall: "Around" does not apply to your "Background" steps
Around will not happen until after a feature's Background has been processed. Use Before and After to avoid that.
Details
Consider this Cucumber feature file:
Feature: Something that needs to be tested
Background:
Given a user
And I sign in
Scenario: Sign out
When I sign out
Then I should see "Signed out"
Scenario: Something else
# ...
Now, assume you have these step definitions:
Around do
puts "** Around: before yield" ...
Casting ActiveRecord scopes or instances to ActiveType extended model classes
When working with ActiveType you will often find it useful to cast an ActiveRecord instance to its extended ActiveType::Record variant.
Starting with active_type 0.4.0 you can use ActiveType.cast for this:
class User < ActiveRecord::Base
...
end
class SignUp < ActiveType::Record[User]
...
end
user = User.find(1)
sign_up = ActiveType.cast(user, SignUp)
sign_up.is_a?(SignUp) # => true
This is basically like [ActiveRecord#becomes](http://apidock.com/rails/v4.2.1/ActiveRecord/Pers…
Linux: Running a single unique instance of command + arguments
run-one is a wrapper script that won't run the given command while another instance of it is running. Is brings several utility commands that offer similar behavior.
```
NAME
run-one - run just one instance at a time of some command and unique set of arguments (useful for cronjobs, eg)
SYNOPSIS
run-one COMMAND [ARGS]
run-this-one COMMAND [ARGS]
run-one-constantly COMMAND [ARGS]
keep-one-running COMMAND [ARGS]
run-one-until-success COMMAND [ARGS]
run-one-until-failure COMMAND [ARGS]
…