Caching in Rails < 6.1 may down parts of your application when using public cache control
Proxy caching is a good feature to serve your publicly visible application content faster and reduce load on your servers. It is e.g. available in nginx, but also affects proxies delivered by ISPs.
Unfortunately, there is a little problem in Rails < 6.1 when delivering responses for different MIME-types. Say you have an arbitrary route in your Rails application that is able to respond with regular HTML and JSON. By sending the specific MIME type in the Accept header, you tell the application to either return HTML (text/html) or JSON (`t...
Nokogiri: How to parse large XML files with a SAX parser
In my case [...] the catalog is an XML that contains all kinds of possible products, categories and vendors and it is updated once a month. When you read this file with the Nokogiri default (DOM) parser, it creates a tree structure with all branches and leaves. It allows you to easily navigate through it via css/xpath selectors.
The only problem is that if you read the whole file into memory, it takes a significant amount of RAM. It is really ineffective to pay for a server if you need this RAM once a month. Since I don't need to n...
New gem: Rack::SteadyETag
Rack::SteadyETag
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is a Rack middleware that generates the same default
ETag
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for responses that only differ in CSRF tokens or CSP nonces.
By default Rails uses
Rack::ETag
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to generate ETag headers by hashing the response body. In theory this would
enable caching
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for multiple requests to the same resourc...
Imagemagick: Batch resize images
Trick: Do not use convert but mogrify:
mogrify -resize 50% *
This overwrites the original image file.
In contrast, convert writes to a different image file. Here is an example if you need this:
cd /path/to/image/directory
for i in `ls -1 *jpg`; do convert -resize 50% $i "thumb_$i"; done
How to send HTTP requests using cURL
-
Reading a URL via GET:
curl http://example.com/ -
Defining any HTTP method (like POST or PUT):
curl http://example.com/users/1 -XPUT -
Sending data with a request:
curl http://example.com/users -d"first_name=Bruce&last_name=Wayne"If you use
-dand do not set an HTTP request method it automatically defaults to POST. -
Performing basic authentication:
curl http://user:password@example.com/users/1 -
All together now:
curl http://user:password@example.com/users/1 -XPUT -d"screen_name=batman"
...
Testing ActiveRecord callbacks with RSpec
Our preferred way of testing ActiveRecord is to simply create/update/destroy the record and then check if the expected behavior has happened.
We used to bend over backwards to avoid touching the database for this. For this we used a lot of stubbing and tricks like
it_should_run_callbacks
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.
Today we would rather make a few database queries than have a fragile test full of stubs.
Example
Let's say your User model creates a first Project on cr...
Updated: Understanding z-index: it's about stacking contexts
There's now a dedicated CSS property for creating a new stacking context
isolation: isolate
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.
ActiveType 2.0 released
We released Active Type Archive 2.0 with breaking changes:
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Casting is prevented when the base record has changes in its already loaded associations, because those would be lost. Option
force: truecan be used to override this and still do the cast (this is not recommended). -
After casting, the base record will not be usable any more. The base record and the newly created casted record share state which is unexpected. Option
force: truecan be used to override this, so the base record is still usa...
JavaScript: Sharing content with the native share dialog
Mobile Chrome and Safari support the "web share API" which allow you to use the native share functionality of an Android or iOS phone. Some desktop OSs like Windows or MacOS also support native share dialogs. See Can I Use Archive for a detailed support matrix.
When clicking a share button using this API, the browser will automatically show all installed applications that support content sharing, such as Whatsapp, Facebook, Twitter, e-mail etc.
The API is extremely simple to use:
if ...
Why your Cucumber feature loses cookies when run under Selenium
When your Cucumber feature seems to forget cookies / sessions when you run it with Selenium check if the test travels in time like here:
Given the date is 2017-10-20
When I sign in
Then I should see "Welcome!"
What happens here is that the Rails application serving pages runs in 2017, but the process running your Firefox or Webkit still lives today. This huge gap in time will expire most Cookies immediately.
If all you need is to freeze the time to a date, a workaround is to travel to the future instead.
Understanding z-index: it's about stacking contexts
The CSS property z-index is not as global as you might think. Actually, it is scoped to a so-called "stacking context". z-indexes only have meaning within their stacking context, while stacking contexts are treated as a single unit in their parent stacking context. This means indices like 99999 should never actually be needed.
Creating a new stacking context
In order to create a stacking context with the least possible side effects, use the
isolation
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property on an...
RSpec: Tagging examples and example groups
In RSpec you can tag examples or example groups with any tags you like simply by saying
describe ReportCreator, slow: true do
# ..
end
describe ReportCreator do
it 'generates reports', slow: true do
# ...
end
end
You can then only run examples with these tags.
rspec --tag slow
rspec -t slow
# Using the parallel_tests gem
rake "parallel:spec[,,--tag slow]"
Or you can run all examples except the ones with a certain tag:
rspec --tag ~slow # note the ~
rspec -t ~slow
# Using the parallel_tests gem
rake "par...
Events triggered by jQuery cannot be observed by native event listeners
jQuery has a function $.fn.trigger(). You can use it to dispatch an event on a jQuery object:
let $element = $('.foo')
$element.trigger('change')
A caveat is that such an event will be received by jQuery event listeners, but not by native event listeners:
let $element = $('.foo')
$element.on('change', event => console.log('I will be called'))
$element[0].addEventListener('change', event => console.log("I WON'T be called"))
$element.trigger('change')
This is not an issue when your entire app is ...