Cancelling the ActiveRecord callback chain
| What | Rails version | Within before_* |
Within after_* |
|---|---|---|---|
| Cancel later callbacks | Rails 1-4 | return false |
return false |
| Cancel later callbacks | Rails 5+ | throw :abort |
throw :abort |
| Rollback the transaction | Rails 1-4 | return false |
raise ActiveRecord::Rollback |
| Rollback the transaction | Rails 5+ | `thr... |
JavaScript: Calling a function with a variable number of arguments
This card describes how to pass an array with multiple element to a JavaScript function, so that the first array element becomes the first function argument, the second element becomes the second argument, etc.
Note how this is different from passing the entire array as the first argument. Compare these two different ways of calling fun() in Ruby:
# Ruby
array = [1, 2, 3]
fun(array) # same as fun([1, 2, 3]) (1 argument)
fun(*array) # same as fun(1, 2, 3) (3 arguments)
Depending on your culture the spreading of array e...
How to use Rails URL helpers in any Ruby class
In Rails 3+, you can use:
class Project
delegate :url_helpers, to: 'Rails.application.routes'
def project_path
url_helpers.project_path(self)
end
end
For Rails 2, use the attached
Modularity
Archive
trait. It will give any Ruby class a method #url_writer, on which you can call URL helpers:
class Foo
does 'write_urls'
def self.class_method
url_writer.session_path
end
def instance_method
url_writer.project_path(5)
end
end
Capybara can find fields by their [aria-label]
Sometimes an input field has no visible label. E.g. a text field with a magnifying glass icon 🔎 and a "Search" button does not really need a visible label "Query".
For
accessibility
Archive
reasons it is good practice to give such a field an [aria-label] attribute:
<input type="search" aria-label="Search contacts">
This way, when a visually impaired user focuses the field, the screen reader will speak the label text ("Search contacts").
Info
Without an
[aria-label]...
Updated: Printing background color of elements
Added that these properties also help keeping text white.
Git shortcut to fixup a recent commit
git --fixup is very handy to amend a change to a previous commit. You can then autosquash your commits with git rebase -i --autosquash and git will do the magic for you and bring them in the right order. However, as git --fixup wants a ref to another commit, it is quite annoying to use since you always have to look up the sha of the commit you want to amend first.
Inspired by the [shortcut to checkout recent branches with fzf](https://makandracards.com/makandra/505126-g...
Ruby: You can nest regular expressions
Ruby lets you re-use existing RegExp objects by interpolating it into new patterns:
locales_pattern = /de|en|fr|es/i
html_tag_pattern = /<html lang="#{locales_pattern}">/
Any modifiers like /i or /x will be preserved within the interpolated region, which is pretty cool. So in the example above only the interpolated locales are case-insensitive, while the pattern around it (/<html .../) remains case-sensitive.
RSpec matcher to compare two HTML fragments
The RSpec matcher tests if two HTML fragments are equivalent. Equivalency means:
- Whitespace is ignored
- Types of attribute quotes are irrelevant
- Attribute order is irrelevant
- Comments are ignored
You use it like this:
html = ...
expect(html).to match_html(<<~HTML)
<p>
Expected content
</p>
HTML
You may override options from CompareXML Archive by passing keyword arguments after the HTML string:
html = ...
expect(html).to match_html(<<~HTML, ignore_text_nodes: true)
...
Enumerators in Ruby
Starting with Ruby 1.9, most #each methods can be called without a block, and will return an enumerator. This is what allows you to do things like
['foo', 'bar', 'baz'].each.with_index.collect { |name, index| name * index }
# -> ["", "bar", "bazbaz"]
If you write your own each method, it is useful to follow the same practice, i.e. write a method that
- calls a given block for all entries
- returns an enumerator, if no block is given
How to write a canonical each method
To write a metho...
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...
Webpack(er): A primer
webpack Archive is a very powerful asset bundler written in node.js to bundle (ES6) JavaScript modules, stylesheets, images, and other assets for consumption in browsers.
Webpacker Archive is a wrapper around webpack that handles integration with Rails.
This is a short introduction.
Installation
If you haven't already, you need to install node.js and Yarn.
Then, put
gem 'webpacker', '~> 4.x' # check if 4.x is still cu...
Git shortcut to checkout recent branches
If you have
fzf
Archive
installed, you may add an alias such as this to your ~/.bashrc:
alias recent-branch="git for-each-ref --sort=-committerdate --format='%(refname:short)' refs/heads/ | fzf | sed 's/\* //g' | xargs -I '{}' git checkout {}"
Now whenever you want to switch back and forth between your most recent branches, type recent-branch, select one and press enter.
Databases don't order rows unless you tell them so
There is no such thing as a "default order" of rows in database tables.
For instance, when you paginate a result set: When using LIMIT, it is important to use an ORDER BY clause that constrains the result rows into a unique order. Otherwise you will get an unpredictable subset of the query's rows. You might be asking for the tenth through twentieth rows, but tenth through twentieth in what ordering? The ordering is unknown, unless you specified ORDER BY.
In Rails, if you use Record.first or Record.last, it will default to orderin...
ActiveRecord: validate_uniqueness_of is case sensitive by default
By default, Rails' validates_uniqueness_of does not consider "username" and "USERNAME" to be a collision. If you use MySQL this will lead to issues, since string comparisons are case-insensitive in MySQL.
(If you use PostgreSQL, read this instead.)
Say you have a user model
class User < ActiveRecord::Base
validates_uniqueness_of :name
end
with a unique index in the database.
If you try to create the users "user" and "USER", this will not trigger a validation error, but may fail with an SQL error due to d...
Large CSS box shadows can bring browsers to a crawl
Browser rendering engines are very slow at rendering large box shadows. I had a situation where a complex layout with fixed elements and large shadows slowed Firefox down to 2 frames/second for scrolling and DOM manipulation.
Some advice:
- Be aware that by introducing fixed elements (e.g. sticky navigation bars) and large animations, you might force the browser to redraw large portions of the site when scrolling. When your fixed elements have shadows, this increases the screen area that needs to be redrawn, which might again require other...
Unpoly 2.4.0 released
- New experimental function
up.history.isLocation()Archive . It returns whether the given URL matches the current browser location Archive . - New experimental function
up.util.normalizeURL()Archive . It returns a normalized version of the given URL string. Two URLs that point to the same resource should normalize to the same string. - Fix a bug where an
[up-nav]Archive link to the root path (/) would never re...