Hello, Thank you for your valuable comment and code.
It looks like I made a change that battery is created in ElectricCar constructor without separate Battery constructor (which indeed was in the book :)), but as the author said - One day you should consider would you use battery on its own or make it part of a car. Anyway our code looks similar although yours feels simpler... <https://play.nim-lang.org/#ix=2Sak> Good material to study. Cheers,
