Instance Methods & self

Behavior lives next to data

A class isn't just a bag of ivars — it's where you put the methods that act on them. price_label computes a display string from @price_per_30_min_cents, the same computed value from Part I's Swift course, and the same one the real backend computes too:

class Walker
  attr_accessor :name, :price_per_30_min_cents

  def initialize(name, price_per_30_min_cents)
    @name = name
    @price_per_30_min_cents = price_per_30_min_cents
  end

  def price_label
    "$#{@price_per_30_min_cents / 100} / 30 min"
  end
end

Say it out loud: this is the exact same idea as Swift's var priceLabel: String { "$\(pricePer30MinCents / 100) / 30 min" } computed property — a value derived from stored data, recalculated fresh on every call, no return needed since it's the method's last expression (implicit return, module 01). And it's also a preview of module 07: once Walker becomes a real ActiveRecord model, this exact method ships unchanged in app/models/walker.rb.