The code I actually wrote ...
prefectures = Prefecture.where(area_id: 3)
cities = City.where(prefecture_id: 13)
Such a code. It's a number that you don't know what the number is when someone other than yourself sees it.
In my head ,,,
3 in area_id is
Kanto
prefecture_id 13 is
Tokyo
I was writing the code as a matter of course.
kantou = Area.find_by(name: 'Kanto')
prefectures = Prefecture.where(area_id: kantou)
tokyo = Prefecture.find_by(name: 'Tokyo')
cities = City.where(prefecture_id: tokyo)
Instead of using numbers, I stored them in variables that anyone can easily see.