Implementing upload progress and remove button with ActiveStorage DirectUpload

DirectUpload allows you to upload files to your file storage without having to wait for the form to submit. It creates AJAX requests to persist the file within your form and wraps them in a little API. This card will show you how to use it in order to create in-place file uploads with progress and a remove button.

This is basic functionality, you may add additional elements, styles and logic to make this look fancy, but the core functionality is the same. I created a file upload that looks like this:

![Image](/makandra/625023/attachments/3...

A "text-wrap: balance" fallback approach

Here is a workaround for when you want to use text-wrap: balance but must also render nicely for browsers that don't support it (mostly Safari <17.5).

Step 1: Put some <br>s into your HTML

First, place explicit line breaks that should work for most cases.
This depends on your use case and is affected by e.g. container widths or user content.

<div class="my-element">
  <p>
    Average score
    <br>
    last month
  </p>
</div>

Step 2: Hide those <br>s when you can balan...

Implementing authentication and authorization for ActiveStorage blobs/files

ActiveStorage does not provide any built-in way of implementing authentication for the available DirectUpload endpoint in Rails. When using DirectUpload as JS wrapper in the frontend, be aware that its Rails endpoint is public by default, effectively allowing anyone to upload an unlimited amount of files to your storage.

The DirectUploadController from @rails/activestorage bypasses your form controller because it uploads the file using an AJAX request that runs directly, before any form roundtrip happens. This is a comfortable solutio...

Rails: Preloading associations in loaded records

Sometimes you want to fetch associations for an ActiveRecord that you already loaded, e.g. when it has deeply nested associations.

Edge Rider gives your models a static method preload_associations. The method can be used to preload associations for loaded objects like this:

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    @user.preload_associations(threads: { posts: :author }, messages: :sender)
  end
end

The attached initializers re...

HTML5: disabled vs. readonly form fields

Form fields can be rendered as noneditable by setting the disabled or the readonly attribute. Be aware of the differences:

disabled fields

  • don’t post to the server
  • don’t get focus
  • are skipped while tab navigation
  • available for button, fieldset, input, select, textarea, command, keygen, optgroup, option

Browser specific behavior:

  • IE 11: text inputs that are descendants of a disabled fieldset appear disabled but the user can still interact with them
  • Firefox: selecting text in a disabled text field is no...

Updated: Automated "git bisect" will make your day

Added methods to keep the line number steady while you time-travel between commits:

How to create a terminal progress indicators in Ruby

For long running scripts it is useful to show a indicator for the progress in the terminal. Alternatively you can use a gem like paul/progress_bar.

count = User.count
index = 0

User.find_each do |user|
  printf("Progress: %.2f%%\r", index.to_f / count * 100)
  user.update!(role: 'member')
  index += 1
end

Preview video

Image

Updated: Jasmine: Creating DOM elements efficiently

I have moved away from creating fixture elements using CSS selectors. While CSS can be very concise, it can be hard to recognize the created elements, and how they are nested within each other.

A more visual alternative is to embed a string of HTML into your test. My specs often have a function htmlFixtures() that parses the HTML and returns a reference to all created elements:

let [list, item1, item2] = htmlFixtures(`
  <ul type="square">
    <li>item 1</li>
    <li>item 2</li>
  </ul>
`)

Because the effective HTML is visible...

How to automatically optimize SVG files with esbuild

SVG files often contain redundant information, like editor metadata or hidden elements. When esbuild handles your static assets, you can easily optimize SVG files using svgo as a plugin. Here is how to do it.

Adding svgo as an esbuild plugin

  1. Add the svgo package to your project's package.json
  2. Adjust your esbuild.config.js like so:
const esbuild = require('esbuild')
const svgo = require('svgo')

const options = {
  // ...
  loader: {
    // ...
    '.svg': 'copy', // this may be different...

Rails: Using PostgreSQL full-text search without a gem

PostgreSQL can cosplay as a full-text search engine. It doesn't have the features or fidelity of ElasticSearch or Algolia, but it's good enough if you just need to search and rank large volumes of text.

This card will teach you how to index, search and rank your Rails models in a PostgreSQL full-text index. We will do this without using any gems aside from ActiveRecord. While there are gems like pg_search or pg_fulltext, manual integration requires very...

Overview of method delegation in Rails

Method delegation in Rails can help you to keep your code organized and avoid deep call chains (law of demeter) by forwarding calls from one object to another. Rails provides several ways to accomplish this. Below is a concise overview of the most common approaches:

Single-Method delegation with delegate

Use the built-in delegate method from ActiveSupport to forward specific methods:

class User < ApplicationRecord
  has_one :profile

  delegate :full_name, :age, to: :profile, prefix: true
end
  • `delegate: full_name, :age...

RSpec: executing specs by example id (or "nesting index")

There are several ways to run a single spec. I usually copy the spec file path with the line number of the example and pass it to the RSpec binary: bin/rspec spec/models/user_spec.rb:30 (multiple line numbers work as well: :30:36:68). Another is to tag the example with focus: true or to run the example by matching its name.

In this card I'd like to ...

Rails: Overwriting default accessors

All columns of a model's database table are automagically available through accessors on the Active Record object.

When you need to specialize this behavior, you may override the default accessors (using the same name as the attribute) and simply call the original implementation with a modified value. Example:

class Poet < ApplicationRecord

  def name=(value)
    super(value.strip)
  end

end

Note that you can also avoid the original setter and directly read/write from/to the instance's attribute storage. However this is dis...

How to not die with ActionView::MissingTemplate when clients request weird formats

When HTTP clients make an request they can define which response formats they can process. They do it by adding a header to the HTTP request like this:

Accept: application/json

This means the client will only understand JSON responses.

When a Rails action is done, it will try to render a template for a format that the client understand. This means when all you are HTML templates, a request that only accepts application/json will raise an error:

An ActionView::MissingTemplate occurred in pages#foo:
  Missing templa...

Flexbox: flex-basis vs. width vs. min-width vs. max-width

Within a Flexbox layout, there are multiple CSS attributes that may affect a child's basis (the initial width before flexing). You might be confused how flex-basis, width, min-width and the intrinsic width of your content play together.

The attached article explains the differences. In summary:

  • If a flex-basis is set, that is used as the basis
  • If no flex-basis is set, the width is used as the basis
  • If neither flex-basis nor width is set, the content...

HTML forms with multiple submit buttons

Most forms have a single submit button that will save the record when pressed.

Sometimes a form needs additional submit buttons like "accept" or "reject". Such buttons usually attempt a state transition while updating the record.

To process a form with multiple buttons, your server-side code will need to know which button was pressed. To do so you can give each submit button a different [formaction] attribute. This will override the ...

Rails routing: Using constraints to avoid "Missing template" errors

You can use constraints in your routes.rb to avoid getting ActionView::MissingTemplate errors when wrong routes are called. Instead, the user will see a 404.

If you want multiple routes to use the same constraint you can use the block syntax:

constraints(format: 'html') do
  resources :pages
  resources :images
end

If you want constraints only on certain routes, you can do:

get '/users/account' => 'users#account', constraints: { format: 'html' }

Tip

You can also avoid this error type through [format con...

Haml Whitespace Preservation (or: Fixing Textarea Indentation in Haml)

Haml renders HTML with indentation reflecting the nesting level of elements. When it comes to white-space preserving content, this may become a problem: the content will be rendered including the HTML indentation.

Problematic: Preserved Indentation

.nest
  %span Reference
  %pre
    = content
<div class="nest">
    <span>Reference</span>
    <pre>
        Hello
        World
    </pre>
</div>

Image

Better: Without Extra Indentation

Render with tilde ~ instead of equal...

Why your Cucumber feature loses cookies when run under Selenium

When your Cucumber feature seems to forget cookies / sessions when you run it with Selenium check if the test travels in time like here:

Given the date is 2017-10-20
When I sign in
Then I should see "Welcome!"

What happens here is that the Rails application serving pages runs in 2017, but the process running your browser still lives today. This huge gap in time will expire most cookies immediately.

If all you need is to freeze the time to a date, a workaround is to travel to the future instead.

Clean code: Avoiding short versions in command options

This card is a general reminder to avoid the short version of a command option in shared code. It's much easier to understand a command and search for an option when it's written out.

You can still use the short version of the options in your own terminal or in code snippets that are more useful when they are very compact. For the latter case you often see a description of the command options one line below e.g. in posts on stackoverflow.

Example good (in code):

/usr/bin/gpg --output password.txt --decrypt password.txt.gpg

...

Git: Restore

tl;dr

git checkout is the swiss army of git commands. If you prefer a semantically more meaningful command for restoring tasks, use git restore instead.

With this command you can ...

  • ... do unstaging - git restore --staged
  • ... discard staged changes - git restore --staged --worktree
  • ... discard unstaged changes - git restore
  • ... restore deleted files - git restore
  • ... restore historic versions - git restore --source
  • ... recreate merge conflicts - git restore --merge
  • ... specifiy...

Capybara: Working with invisible elements

When Capybara locates elements in the DOM, by default it allows only accessing visible elements -- when you are using a driver that supports it (e.g. Selenium, not the default Rack::Test driver).

Consider the following HTML:

<div class="test1">One<div>
<div class="test2">Two</div>

With some CSS:

.test1 { display: block }
.test2 { display: none }

We will be using Capybara's find below, but this applies to any Capybara finder methods.

Default: visible: :visible

As described above, by default Capybara finds ...

Defining and calling lambdas or procs (Ruby)

Ruby has the class Proc which encapsulates a "block of code". There are 2 "flavors" of Procs:

  • Those with "block semantics", called blocks or confusingly sometimes also procs
  • Those with "method semantics", called lambdas

lambdas

They behave like Ruby method definitions:

  • They are strict about their arguments.
  • return means "exit the lambda"

How to define a lambda

  1. With the lambda keyword

    test = lambda do |arg|
      puts arg
    end
    
  2. With the lambda literal -> (since Ruby 1.9.1)
    ...