ruby 42 lines · 7 steps

Building a weekly signups report in Rails

A plain service object that groups records by week and fills in zeros for weeks with no signups.

Explained by highlit

Rails Intermediate service object aggregation group by date bucketing dependency injection

1class WeeklySignupsReport
DEFAULT_WEEKS = 12
3 
def initialize(weeks: DEFAULT_WEEKS, source: User.all)
  @weeks = weeks
  @source = source
end
8 
def call
  labels = week_starts
  counts = counts_by_week
12 
  labels.map do |week_start|
    {
      week: week_start.strftime("%b %-d"),
      starts_on: week_start.iso8601,
      signups: counts.fetch(week_start, 0)
    }
  end
end
21 
private
23 
attr_reader :source
25 
def counts_by_week
  source
    .where(created_at: range)
    .group("DATE_TRUNC('week', created_at)")
    .count
    .transform_keys { |timestamp| timestamp.to_date }
end
33 
def week_starts
  (0...@weeks)
    .map { |offset| range.begin.to_date + offset.weeks }
end
38 
def range
  @range ||= @weeks.weeks.ago.beginning_of_week..Time.current.end_of_week
end
42end

01 / 01

STEP 01

Walkthrough

Space play ←→ step click any line

Three takeaways

1Injecting the source relation makes the report reusable and easy to test with any scope.
2Grouping in SQL with DATE_TRUNC pushes aggregation to the database instead of loading every row.
3Building a complete list of buckets and defaulting missing keys to zero guarantees a gap-free series.

Related explainers

ruby

require "shellwords"
require "open3"
 
module Backup

Building safe shell commands in Ruby

shell-out subprocess command-injection

Intermediate 7 steps

php

<?php
 
namespace App\Services\Checkout;

Validating coupons with Laravel's Pipeline

pipeline chain of responsibility transactions

Intermediate 7 steps

ruby

class UserAgentParser
  BROWSERS = [
    [/Edg\/([\d.]+)/, "Edge"],
    [/OPR\/([\d.]+)/, "Opera"],

Parsing user-agent strings in Ruby

regex pattern-matching lookup-tables

Intermediate 8 steps

ruby

class LogAggregator
  BUCKET_FORMAT = "%Y-%m-%dT%H:%M"
 
  def initialize(entries)

Bucketing log entries by the minute in Ruby

aggregation hashing enumerable

Intermediate 5 steps

php

<?php
 
namespace App\Services;

Building a cached daily leaderboard in Laravel

caching aggregation eager-loading

Intermediate 9 steps

ruby

class ApplicationController < ActionController::Base
  EXPERIMENTS = {
    checkout_button_color: %w[control blue green],
    onboarding_flow: %w[control streamlined]