When paginating records, we usually need to know the number of total records in order to render pagination links. Popular pagination libraries like will_paginate Archive or Kaminari Archive do this for us by simply issuing an extra query, like this:

SELECT post.* FROM posts LIMIT 20 OFFSET 100;

SELECT COUNT(*) FROM posts;   

This is fine most of the time. But rarely, you might have very complicated WHERE conditions or a subquery that takes time to run. In thes...

You can use the code below to check whether the browser can make connections to the current site:

await isOnline() // resolves to true or false

Limitations of navigator.onLine

While you can use the built-in function navigator.onLine Archive (sic), it is only a hint for whether the device can access the Internet.

When navigator.onLine === false you know for certain that the user device has no connection to the Internet. This mea...

Ruby has two different ways to match the start and the end of a text:

• ^ (Start of line) and $ (End of line)
• \A (Start of string) and \z (End of string)

Most often you want to use \A and \z.

Here is a short example in which we want to validate the content type of a file attachment. Normally we would not expect content_type_1 to be a valid content type with the used regular expression image\/(jpeg|png). But as ^ and $ will match lines, it matches both content_type_1 and content_type_2. Using \A and \z will wo...

Somewhat regularly, you will need to filter a list down to some items and then map them to another value.

You can of course chain map and compact, or select/filter and map, but Ruby 2.7 introduced a method for this exact purpose: filter_map Archive .

So instead of

>> [1, 2, 3, 4, 5, 6].map { |i| i * 2 if i.even? }.compact
=> [4, 8, 12]

or

>> [1, 2, 3, 4, 5, 6].select(&:even?).map { |i| i * 2 }
=> [4, 8, 12]

you can just do

>> [1,...

Spreewald Archive comes with a selector_for helper that matches an English term like the user's profile into a CSS selector. This is useful for steps that refer to a particular section of the page, like the following:

Then I should see "Bruce" within the user's profile
                                 ^^^^^^^^^^^^^^^^^^

If you're too lazy to manually translate English to a CSS selector by adding a line to features/env/selectors.rb, we already have an [auto-mapper to translate English into ...

Sometimes huge refactorings or refactoring of core concepts of your application are necessary for being able to meet new requirements or to keep your application maintainable on the long run. Here are some thoughts about how to approach such challenges.

Break it down

Try to break your refactoring down in different parts. Try to make tests green for each part of your refactoring as soon as possible and only move to the next big part if your tests are fixed. It's not a good idea to work for weeks or months and wait for all puzzle pieces ...

When changing code in mailers, updating the corresponding mailer preview is easily forgotten.

Mailer previews can be tested like other code as well and I sometimes add the following test to test suites:

# Make sure to require the previews
Dir[Rails.root.join('test/mailers/previews/*.rb')].sort.each { |file| require(file) }


ActionMailer::Preview.all.index_with(&:emails).each do |preview, mails|
  mails.each do |mail|
    it "#{preview}##{mail} works" do
      expect { preview.call(mail) }.not_to raise_error
   ...