Usually you add errors to :base in ActiveRecord, in case no appropriate attribute could be used to add the error.
Simple Form doesn't render errors on :base by default, but here a few options how you can render these on demand. For all the options below we use the following example with a Simple Form Bootstrap configuration:
- @user = Backend::User.new
- @user.errors.add(:base, 'First error')
- @user.errors.add...
Capybara has a variety of finder methods like find_button to help you look up DOM elements. There are also matchers like have_field to make expectations during tests.
These methods also have a number of options to influence the lookup. E.g. the :disabled option lets you control whether Capybara will match disabled fields.
If you have a matching condition that cannot be expressed by the existing Capybara opt...
Maintaining larger projects makes it more difficult to balance refactoring and upgrade tasks according to its actual value. Consider to create and periodically maintain a summary, which helps you and your team in the decision which refactoring task should be taken next.
Here is an template on how you might categorize your tasks:
| Technical debt | Estimated Efforts | Customer value| Customer value explained| Developer value|Developer value explained|
|-----------------------------|----------------|-----------|------...
PostgreSQL's Common Table Expressions (CTEs) can be used to extract sub-queries from bulky SQL statements into a temporary table to be referenced instead.
This is most useful to avoid ugly joins or sub-selects. CTEs can be used for SELECT, INSERT, UPDATE or DELETE.
Example (from the PostgreSQL docs):
WITH regional_sales AS (
SELECT region, SUM(amount) AS total_sales
FROM orders
GROUP BY region
), top_regions AS (
SELECT region
FROM regional_sales
WHERE total_sales > (SE...
When you use Sentry to monitor exceptions, an important feature is Sentry's error grouping mechanism. This will aggregate similar error "events" into one issue, so you can track and monitor it more easily. Grouping is especially important when you try to silence certain errors.
It is worth understanding how Sentry's grouping mechanism works.
The exact algorithm has changed over time, and Sentry will keep using the algorithm t...
Spammers have started abusing other application to send their spam. This works like this:
Potentia...
When you use native smooth scrolling there is no built-in method to detect the end of the scrolling animation. Methods like scrollTo() don't return a promise. We will eventually get a scrollend event, but that is still some time away.
Until then I'm using the following `awaitScrollE...
By default most exceptions in Rails will render a 500 error page and will create a new issue in your error monitoring. There are some built-in rules in Rails that
A good example is ActiveRecord::NotFound: You don't want an exception in your error monitoring when users navigate to e.g. a blog post t...
The Truemail gem (not to be confused with truemail.io) allows validating email addresses, e.g. when users enter them into a sign-up form. It runs inside your application and does not depend on an external SaaS service.
Truemail supports different validation "layers":
Headless Chrome is a way to run the Chrome browser without a visible window.
Configure the Capybara driver like this:
Capybara.register_driver :selenium do |app|
options = Selenium::WebDriver::Chrome::Options.new
unless ENV.key?('NO_HEADLESS')
options.add_argument('--headless')
options.add_argument('--disable-gpu')
end
if ENV.key?('CI')
options.add_argument('--no-sandbox')
options.add_argume...
Browsers' printing methods usually don't print background colors. In most cases this is the desired behavior, because you don't want to spend tons of ink printing the background of a web page. But in some cases you want to print the background color of elements, e.g. bars of a chart. For those elements you need to set the following CSS styles:
-webkit-print-color-adjust: exact; /* Chrome and Safari */
color-adjust: exact; /* Firefox */
Another case is printing of white text. When removing background colors, chances are white text n...
When storing floating-point numbers such as prices or totals in an SQL database, always use a DECIMAL column. Never use FLOAT or kittens will die.
DECIMAL columns are parametrized with a precision and a scale. These parameters describe which numbers can be stored in that column. E.g. a decimal with a precision of 5 and a scale of 2 can store numbers from -999.99 to 999.99, but not 1000 or 1.234.
This card explains what various databases do when you try to store a number in a DECIMAL field, and that number exceeds that colum...
This card compares patterns to store trees in a relation database like MySQL or PostgreSQL. Implementation examples are for the ActiveRecord ORM used with Ruby on Rails, but the techniques can be implemented in any language or framework.
We will be using this example tree (from the acts_as_nested_set docs):
root
|
+-- Child 1
| |
| +-- Child 1.1
| |
| +-- Child 1.2
|
+-- ...
In contrast to RSpec's included allow_value matcher, the attached matcher will also work on associations, which makes it ideal for testing assignable_values.
describe Unit do
describe '#building' do
it 'should only allow buildings that a user has access to' do
building = build(:building)
other_building = build(:building)
unauthorized_building = build(:building)
power = Power.new(build(:user))
Power.with_power(power) do
expect(power).to receive(:buildings).at_least...
Rails Active Support provides some helpful methods for calculating times and dates, like Duration#ago or Duration#from_now. But beware when using those, because they wont give you Dates or Times but ActiveSupport::TimeWithZone instances. As the class name hints, you now have to be awa...
Rails offers a way to prepend (or append) view paths for the current request. This way, you can make the application use different view templates for just that request.
A use case of this is a different set of view templates that should be used under certain circumstances:
class UsersController < ApplicationController
before_action :prepare_views
def index
# ...
end
private
def prepare_views
if <condition>
prepend_view_path Rails.root.join('app', 'views', 'special')
end
end
...
Geordi provides a pretty neat way to generate beautiful commit messages according to your stories in Pivotal Tracker:
geordi commit
Geordi reads from a .geordi.yml file inside your repo and connects to Pivotal Tracker to list started and finished stories with their title. Choosing one of them generates a commit message including id and title from pivotal tracker. For example:
[#1234567] CRUD Users
If you encounter a bug like `40...
Cross-Site Request Forgery (CSRF) is an attack pattern for websites. A CSRF attack is usually relevant in a browser context, where state is kept for multiple domains (as opposed to independent requests made e.g. with curl). The most common example is authentication via cookies. If a script on https://example.com made requests to https://docs.google.com, the browser would send all cookies for docs.google.com along, effectively given the script access to anythin...
Rails offers the fresh_when method to automatically compute an ETag from the given record, array of records or scope of records:
class UsersController < ApplicationController
def show
@user = User.find(params[:id])
fresh_when @user
end
def index
@users = User.all.to_a
fresh_when @users
end
end
When your view also displays other records (typically associations), those other records should be included in the ETag. You can do so by passing an array of ETaggable objects to fresh_when.
...
By activating strict_loading you force developers to address n+1 queries by preloading all associations used in the index view. Using an association that is not preloaded will raise an ActiveRecord::StrictLoadingViolationError.
I think it's a good default to activate strict_loading in your controllers' #index actions. This way, when a change introduces an n+1 query, you...
Testing your responses in Rails allows to parse the body depending on the response MIME type with parsed_body.
get '/posts.json'
response.parsed_body # => [{'id' => 42, 'title' => 'Title'}, ...]
For JSON APIs we often parse the response as symbolized keys with JSON.parse(response.body, symbolize_names: true), which is not supported by parsed_body. For all other cases you might want to drop JSON.parse(response.body) and replace it w...
Migrating data from a legacy into a new system can be a surprisingly large undertaking. We have done this a few times. While there are significant differences from project to project, we do have a list of general suggestions.
Before you start, talk to someone who has done it before, and read the following hints:
Before any technical considerations, you need to understand the old system as best as possible. If feasible, do not only look at its API, or database, or frontend, but let a user of the old system sho...
Our applications not only need to be functional, they need to be fast.
But, to quote Donald Knuth,
premature optimization is the root of all evil (or at least most of it) in programming
The reasoning is that you should not waste your time optimizing code where it does not even matter. However, I believe there are some kinds of optimizations you should do right away, because
This is an attempt to list some of those things:
...
We will achieve this by creating a block accepting method to optionally create and then lock a .lock File of the underlying accessed file.
Why create a .lock file?
.lock file is that #flock might block some operations and require the index node of the file to be consistent. Some operations might change that index node.