Every iOS app I've shipped over the last nine years started the same way: a Rails developer with a great web app, users who want it in the App Store, and weeks spent on Xcode, signing certificates, and Swift boilerplate that has nothing to do with the actual product.
The main reason for Ruby's drop is Python's popularity. There is no need for Ruby anymore. Ruby was the Tiobe language of the year in 2006, having displayed the highest growth rate in popularity that year, it is now close to dropping out of the top 30, according to Tiobe CEO Paul Jansen.
The core idea is three separate attribute layers: inputs (what comes in), internals (working state), and outputs (what goes out). Each is a distinct declaration with its own namespace and type checking. Combined with declarative make calls that define action order, the data flow through a service is visible at a glance: class Payments::Process < ApplicationService::Base input :payment, type: Payment internal :charge_result, type: Servactory::Result output :payment, type: Payment make :validate_status! make :perform_request! make :handle_response! make :assign_payment
