When doing some meta-programming magic and you want to do something for all attributes of a class, you may need to access connection or some of its methods (e.g...
...will encounter fun errors such as: PG::ConnectionBad (for missing databases on PostgreSQL) ActiveRecord::StatementInvalid: PG::UndefinedTable (when database exists, but has no tables) Generally speaking, evaluating model columns during...
...come across objects created by some gem or framework. You don't have the source code at hand, still need to inspect this object. Here are some tools to do...
...from Object. This makes the methods list drastically more relevant. You can also try subtracting other base classes like ActiveRecord::Base.methods etc. To further narrow it down you can also...
Sometimes you have a file that is related to a project, while not actually being part of it. You'd like to keep them around, but others won't need...
...them – e.g. some notes, a log, or a database dump. Sure, you have a project directory – but all of it is tracked by Git. A project's tmp/ directory is...
...tell npm to install a package globally with npm -g install @puppeteer/browsers. However, it seems that its not possible that npx can run commands from global packages without referencing the...
...image, where a testing chrome and chromedriver is installed with a global npm package. Since there is no local project it was more useful to install the package in a...
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
Module imports are hoisted (internally moved to the beginning of the current scope). Therefore, it doesn’t matter where you mention them in a module and the following...
Footgun example When you're not aware of import hoisting you may be surprised that your code runs in a different order than you see in the source file...
In the past we validate and set default values for boolean attributes in Rails and not the database itself. Reasons for this: Older Rails didn't support database defaults when...
...the Rails upstream on constraints in the database, is adding default values in the schema of the database itself. We also encourage to set boolean attributes to not null. For...
...that's not a float! This occurs because JavaScript uses double precision floats to store numbers. So according to IEEE floating point definition only numbers between...
...and 2^53 - 1 (9007199254740991) can safely be represented in JavaScript. Note that ECMAScript 6 will probably also offer Number.MAX_SAFE_INTEGER (and Number.MAX_SAFE_INTEGER) that point to those...
...in development. Note that there are services like badssl.com to test against weird SSL behavior. Self-signed certificates Talking to a host using a self-signed certificate will fail because...
...the certificate can not be verified. >> RestClient.get('https://self-signed.badssl.com/') RestClient::SSLCertificateNotVerified: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed Self-signed certificates...
...discouraged to load your JavaScript by a tag in the : The reason is that a tag will pause the DOM parser until the script has loaded and executed. This will delay the browser's first contentful paint. A much better default is to load your scripts with a tag: A deferred script has many useful properties: It does not block the browser from rendering content. Deferred scripts...
...can query the entire DOM tree with querySelector() and friends. document.readyState is 'interactive'. Deferred scripts will run before the DOMContentLoaded event. That means if your code waits to initialize until...
...not necessary to add a version constraint next to your gems in the Gemfile. Since all versions are saved in the Gemfile.lock, everyone running bundle install will get exactly the...
...You are not checking in the Gemfile.lock into the version control (not recommended) A specific gem has a bug in a more recent version (adding a comment for the reason...
By default, Devise sends all emails synchronously with deliver_now. To change that, Devise's readme suggests overwriting the send_devise_notification method like this: class User def send_devise...
...notification(notification, *args) devise_mailer.send(notification, self, *args).deliver_later end end However, there is one problem: When deliver_later enqueues the mail with ActiveJob, the job arguments are logged. In...
Compiling Sass is probably the slowest part of your build, so this is worth a try if you're using Sass...
...If you're using the sass npm package to compile your SASS/SCSS, consider switching to sass-embedded. It should be a drop-in replacement in a large app and it...
Ubuntu 18.04 uses systemd to manage services. There are basically two commands for listing all services and manipulating the state of a certain service: service and systemctl: service manages System...
...which system V init scripts are available and running / not running, you can use service --status-all: >service --status-all [ + ] acpid [ - ] alsa-utils [ - ] anacron [ + ] apache-htcacheclean [ - ] apache2 [ + ] apparmor [ + ] apport
The change_column method for rails migrations support casting with a custom SQL statement. This allows us to change a column type and keep the former content as the new...
...number, 'int USING CAST(rating AS int)' end end Warning This migration's rollback strategy will fail, if any existing entry can't be casted. This is likely to happen...
When your public-facing application has a longer downtime for server maintenance or long migrations, it's nice to setup a maintenance page to inform your users. When delivering the...
...maintenance page, be very careful to send the correct HTTP status code. Sending the wrong status code might get you kicked out of Google, or undo years of SEO work...
...group using Ruby's def keyword or define_method method: describe "example" do def sum(a, b) a + b end it "has access to methods defined in its group" do...
...expect(sum(3, 4)).to be(7) end end The helper method is also available to groups nested within that group. The helper method is not available to parent or...
...yml files. You may override those application-wide error messages using model or attribute scope like this: en: activerecord: errors: messages: invalid: is invalid # used for any invalid attribute in...
There is a practical short list for valid/invalid example email addresses - Thanks to Florian L.! The definition for valid emails (RFC 5322) can be unhandy for some reasons, though.
...provides a built-in email regex URI::MailTo::EMAIL_REGEXP. That's the best solution to work with. /\A[a-zA-Z0-9.!\#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0...
To work with other type of nodes (like text, comment or CDATA sections) you need to: Retrieve child nodes contents() (which behaves like children() except that it returns...
...element and returns an array of all child nodes that are text nodes: function selectTextNodes($container) { return $container.contents().filter(function() { return this.nodeType === 3; }); } Also check out this list of existing...
If you migrate a Rails application from Sprockets to Webpack(er), you can either transpile your CoffeeScript files to JavaScript or integrate a CoffeeScript compiler to your new process. This...
...to the global namespace, define them on window directly: -class @User +class window.User Replace Sprocket's require statement with Webpacker's import statement to load dependencies. -#= require ./person +import './person...
...PATH << File.expand_path('../../lib', __FILE__) require 'my_cli' MyCli.run! However, if you create a symlink to this file, this will no longer work. __FILE__ will resolve to the path of...
...the symlink, not to its target. One solution is to use File.realpath(__FILE__). In Ruby 2+ you can also use this: $LOAD_PATH << File.expand_path('../lib', __dir__) __dir__ is simply...
Download buttons can be difficult to test, especially with Selenium. Depending on browser, user settings and response headers, one of three things can happen: The browser shows a "Save as...
...dialog. Since it is a modal dialog, we can no longer communicate with the browser through Selenium. The browser automatically downloads the file without prompting the user. For the test...
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, your...