form_with multipart data

This whole time I thought I needed to do this for supporting files in forms:

  form_with(model: attachment, html: { enctype: "multipart/form-data"} ) 

but it turns out you can actually just do this:

form_with(model: attachment, multipart: true)

which is cleaner and easier to remember.

When to use DB Indexes

Indexes are something I don’t really think about a lot, but know that they can have dramatic impacts on performance.

A good rule of thumb is to create database indexes for everything that is referenced in the WHERE, HAVING and ORDER BY parts of your SQL queries. — Igor Šarčević

You should pretty much add indexes to all foreign keys.

An index for a certain column/columns in a database works similarly to an index in a book. Instead of scanning every page of a book for all instances of a subject, we flip to the index, which is usually alphabetized in some fashion, and find the subject in there. The subject entry points us to the relevant pages of the book. — source

Another case is for uniqueness.

For example, if a users table has a uniqueness validation for combination email and username.

(i.e. there cannot be more than one user with the same email/username combo)

Indexing the email attribute will allow our database to abort any save operation on a non-unique email, giving us a second line of defense against the wild users of your site.

add_index :table_name, [:column_name_a, :column_name_b], unique: true

source

Ruby Refinements

Whenever I’ve had a predifined class and wanted to add/modify a method to it, I’ve always patched it or seen people make a Concern or something.

Apparently, Ruby has a built in thing for this exactly that is better called Refinements.

# Instead of a monkey patch

class String
  def to_a
    return [] if blank?

    str = dup
    str.slice!("[")
    str.slice!("]")
    str.split(",")
  end
end

# Do this instead


module StringToArray
  refine String do
    def to_a
      return [] if blank?

      str = dup
      str.slice!("[")
      str.slice!("]")
      str.split(",")
    end
  end
end

# Then in module or class that you use it
module ResourceCreator
  using StringToArray
end

• Mastering refinements in Ruby
• Ruby Refinements

Git Bisect

Binary search through your git log to find where you hecked up and introduced a bug.

This command saved my life. I was trying to debug a really silly error that I couldn’t debug with error messages because the issue happened because a method was added to a core class and the stacktrace was not helpful. git bisect was the ONLY thing that worked.

Video I watched:

Notes

git bisect start
git bisect bad          # marks current commit doesn't work
git bisect good d0bf3f6 # specify latest commit that *does* work

# for each commit given, mark bad or good with
git bisect bad
git bisect good
# when done,
git bisect reset

Aside: embed videos in markdown with: https://markdown-videos.jorgenkh.no/

Bootstrap Modal with Dynamic Content

For context, I was working on a feature to to allow users to preview the associated thread (in a modal) of each notification from the notifications index page. While the notifications were paginated, the post threads could be very large. The naive approach of just having a modal for each notification was very ineffecient when threads were large and made the page load slow.

To increase the performace, I wanted to render just one modal and have the content change depending on which notification was clicked.

This was a little tricky to get timings right for when and what content to load, but this article helped me a lot.

https://philonrails.substack.com/p/loading-dynamic-content-on-opening

Eventually I added an auto-scroll to the exact part of the thread that was related to the notification to.