Building web applications: Beyond the happy path
When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.
Different screen sizes and browsers
Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?
- Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
- Use @media queries to build a responsive design
- If you do not suppo...
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...
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...
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...
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...
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...
About IE's Compatibility mode
IE has a "Compatibility Mode" for old browsers. You can keep IE from offering it (and fix some other things, too) by adding this meta tag to your <head>:
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
Or in Haml:
%meta(http-equiv="X-UA-Compatible" content="IE=Edge")
However, there are some things you need to bear in mind:
-
X-UA-Compatible is ignored unless it's present inside the first 4k of you page. If you put it somewhere in the bottom of your head section (or in the body) move it to top. The best place for ...
How to test whether your device has a true Retina display
The linked site hosts a simple test. It shows two images with narrow vertical/horizontal lines. The more they resemble each other, the more Retina your display is.
PostgreSQL and its way of sorting strings
PostgreSQL uses the C library's locale facilities for sorting strings:
- First, all the letters are compared, ignoring spaces and punctuation.
- It sorts upper and lower case letters together. So the order will be something like
a A b B c C - Then, spaces and punctuation are compared to break ties.
Example:
| Ruby | PostgreSQL |
|---|---|
| IMAGE3.jpg | image2.jpg |
| image.jpg | image3.jpg |
| image2.jpg | IMAGE3.jpg |
| image3.jpg | image.jpg |
Further reading
- [PostgreSQL-FAQ: Why do my strings sort incorrectly?](h...
Tasks, microtasks, queues and schedules - JakeArchibald.com
The way that Javascript schedules timeouts and promise callbacks is more complicated than you think. This can be the reason why callbacks are not executed in the order that they are queued.
Please read this article!
This is an extract of the example in the article which demonstrates the execution order of tasks and microtasks.
console.log('script start');
setTimeout(function() {
console.log('setTimeout');
}, 0);
Promise.resolve().then(function() {
console.log('promise1');
}).then(function() {
console.log('promise2');
})...
How to organize monkey patches in Ruby on Rails projects
As your Rails project grows, you will accumulate a number of small patches. These will usually fix a bug in a gem, or add a method to core classes.
Instead of putting many files into config/initializers, I recommend to group them by gem in lib/ext:
lib/
ext/
factory_girl/
mixin.rb
carrierwave/
change_storage.rb
fix_cache_ids.rb
sanitize_filename_characters.rb
ruby/
range/
covers_range.rb
array/
dump_to_excel.rb
xss_aware_join.rb
enumerable/
...
Dynamically uploading files to Rails with jQuery File Upload
Say we want …
- to create a
Gallerythat has a name andhas_many :images, which in turn have a caption - to offer the user a single form to create a gallery with any number of images
- immediate uploads with a progress bar per image
- a snappy UI
Enter jQuery File Upload. It's a mature library that can do the job frontend-wise. On the server, we'll use Carrierwave, because it's capable of caching images.
(FYI, [here's how to do the u...
UI Sortable on table rows with dynamic height
UI sortable helps reordering items with drag 'n drop. It works quite fine.
Proven configuration for sorting table rows
When invoking the plugin, you may pass several options. This set is working fine with table rows:
$tbody.sortable # Invoke on TBODY when ordering tables
axis: 'y' # Restrict drag direction to "vertically"
cancel: 'tr:first-child:last-child, input' # Disable sorting a single tr to prevent jumpy table headers
containment: 'parent' # Only drag within this container
placehol...
Testing Cookie Limits
TL;DR If you want to support most browsers, then don't exceed 50 cookies per domain, and don't exceed 4093 bytes per domain (i.e. total size of all cookies <= 4093 bytes)
Behind the link, you'll find a simple HTML page that offers some cookie tests (how large, how many etc) and an overview of this data for various browsers.
Fun fact: You cannot delete cookies with a key that hits the size limit and has a small value.
How to inspect RSS feeds with Spreewald, XPath, and Selenium
Spreewald gives you the <step> within <selector> meta step that will constrain page inspection to a given scope.
Unfortunately, this does not work with RSS feeds, as they're XML documents and not valid when viewed from Capybara's internal browser (e.g. a <link> tag cannot have content in HTML).
Inspecting XML
If you're inspecting XML that is invalid in HTML, you need to inspect the page source instead of the DOM. You may use Spreewald's "... in the HTML" meta step, or add this proxy step fo...
RSpec: Scoping custom matchers to example groups
When you find yourself in the situation that you would like to define a custom matcher in your specs, but you do not want to define a global matcher since you need it only for your specific test, there are two ways to do it:
Custom matcher for a single group
If you're only going to include a matcher once, you can also use the matcher macro within an example group:
describe "group" do
matcher :be_just_like do |expected|
match {|ac...
Delay your Jasmine tests until the document is ready
To delay your entire Jasmine test suite until the DOM is ready, add the following:
beforeAll(function(done) {
$(done);
});
thoughtbot/fake_stripe: A Stripe fake so that you can avoid hitting Stripe servers in tests.
fake_stripe spins up a local server that acts like Stripe’s and also serves a fake version of Stripe.js, Stripe’s JavaScript library that allows you to collect your customers’ payment information without ever having it touch your servers. It spins up when you run your feature specs, so that you can test your purchase flow without hitting Stripe’s servers or making any external HTTP requests.
We've also had tests actually hitting the testing sandbox of Stripe, which worked OK most of the time (can be flakey).
How to fix: "rake db:rollback" does not work
When you run rake db:rollback and nothing happens, you are probably missing the latest migration file (or have not migrated yet).
$ rake db:rollback
$
If that happens to you, check your migration status.
$ rake db:migrate:status
up 20160503143434 Create users
up 20160506134137 Create pages
up 20160517112656 Migrate pages to page versions
up 20160518112023 ********** NO FILE **********
When you tell Rails to roll back, it tries to roll back the latest change that was mi...
How to explain SQL statements via ActiveRecord
ActiveRecord offers an explain method similar to using EXPLAIN SQL statements on the database.
However, this approach will explain all queries for the given scope which may include joins or includes.
Output will resemble your database's EXPLAIN style. For example, it looks like this on MySQL:
User.where(id: 1).includes(:articles).explain
EXPLAIN for: SELECT `users`.* FROM `users` WHERE `users`.`id` = 1
+----+-------------+-------+-------+---------------+
| id | select_type | table | type | possible_keys |
+----+-----...
How to Work With Time Zones in Rails
When dealing with time zones in Rails, there is one key fact to keep in mind:
Rails has configurable time zones, while
Ruby is always in the server's time zone
Thus, using Ruby's time API will give you wrong results for different time zones.
"Without" time zones
You can not actually disable time zones, because their existence is a fact. You can, however, tell Rails the only single time zone you'll need is the server's.
config.time_zone = "Berlin" # Local time zone
config.active_record.default_timezone = :loca...
RSpec: Expecting non-primitive objects as method invocation arguments
Expecting a primitive value as an argument to a method invocation is easy:
expect(object).to receive(:foo).with('arg1', 'arg2')
This expectation would be met with this call:
object.foo('arg1', 'arg2')
But what if the argument is expected to be an object with a given set of methods? E.g. this class with #first_name and #last_name methods:
class Person
def initialize(first_name, last_name)
@first_name = first_name
@last_name = last_name
end
attr_reader :first_name, :last_name
end
``...