5 posts by obie-fernandez

Is it possible to render a "sidecar" partial for a ViewComponent?

Let's say I have

class MyComponent < ViewComponent::Base

and 2 view files in


In my_component.html.erb, I want to be able to do:

render "some_partial"

But without a special configuration, that looks under the views directory for said partial. I don't want to extract that partial to its own component, nor do I want it floating by itself in the view directory.

The first step is to tell Rails it can look for templates in the view components directory

class ApplicationController < ActionController::Base
  append_view_path "#{Rails.root}/app/components"

Keep in mind that view contexts are based on the currently executing controller, so <%= render :some_partial %> in a PostsController (even within a ViewComponent class) will look for a partial in a subdirectory /posts or /application.

To make sure Rails finds your partial, use an absolute path when you render it:

<%= render "/my_component/some_partial" %>

Hat tip to Roli in the StimulusReflex discord

Learned by obie-fernandez on Mar 10, 2021

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Turbo Native wrappers are generally available and working well

I've been waiting for updates to this technology for a long time and today found out that it's already available.

The website is here: https://turbo.hotwire.dev/handbook/native

And there's a cool blog post about it here: https://blog.minthesize.com/turbo-native

Learned by obie-fernandez on Mar 1, 2021

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Strip and downcase email addresses if you're using them as lookup keys for anything

Seems like something I need to learn every few years, and recently popped up on one of my side projects. If you're relying on email addresses as lookup keys, for instance in authentication/login scenarios, then standardize on lowercase and strip whitespace for good measure.

This came up when a customer was not able to get inbound email processing to work for his account. Turns out that his user record had a properly downcased email, but his SMTP server was sending his email address with capitalization. Some string massaging fixed the immediate issue.

User.find_by(email: reply_params["sender"].to_s.downcase)

After putting this fix in, I found everywhere else in the system that email addresses come in as input and gave them the same treatment.

Learned by obie-fernandez on Feb 17, 2021

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Migration operation that should run only in one direction

Disclaimer: I know it's not recommended to do data mutation in schema migrations. But if you want to do it anyway, here's how you do a one-way operation, using the reversible method.

class AddAds < ActiveRecord::Migration[5.0]
  def change
    create_table :ads do |t|
      t.string :image_url, null: false
      t.string :link_url, null: false
      t.integer :clicks, null: false, default: 0

    reversible do |change|
      change.up do
        Ad.create(image_url: "https://www.dropbox.com/s/9kevwegmvj53whd/973983_AdforCodeReview_v3_0211021_C02_021121.png?dl=1", link_url: "http://pages.magmalabs.io/on-demand-github-code-reviews-for-your-pull-requests")

Learned by obie-fernandez on Feb 16, 2021

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Monthly streak display using SQL CTE in Rails

How to make a streak display like 750words.com


The database can do the heavy lifting for this kind of thing. A CTE (Common Table Expression) in a WITH clause to give me the set of days of the month that I would fill in with the completion data using a LEFT JOIN to make sure I got rows back even when there was no corresponding data on the right side.

# app/models/streak.rb
Streak = Struct.new(:user, :date) do
  # If you're wondering why we didn't use class extension syntax of Struct see the following link
  # https://tiagoamaro.com.br/2016/03/05/superclass-mismatch-structs-and-unicorn/
  SQL = "WITH dates(d) AS (
            SELECT generate_series(
              (date ?)::timestamp,
              (date ?)::timestamp,
              interval '1 day')
            SELECT dates.d::date created_at, count(e.id) count FROM dates
            LEFT JOIN entries e on dates.d::date = e.created_at::date AND e.user_id = ?
            GROUP BY dates.d::date
            ORDER BY dates.d::date"

  def calendar
    Entry.find_by_sql([SQL, date.beginning_of_month, date.end_of_month, user.id])

I'm knowingly abusing ActiveRecord by shoving the data I want to represent into Entry objects. I can be kinder to my future self and other maintainers by subsequently wrapping the returned objects into something more descriptive like StreakMonth or whatever.

Learned by obie-fernandez on Feb 10, 2021

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