Capter 6: userManager appear suddenly

While reading the book, it tells me to write code under userManager.
But at that point the userManager is nowhere to be found.
I read Chapter 6 again just in case.
But the userManager doesn’t appear anywhere.
Where the hell did this code come from?

Chapter 6, page 136.

스크린샷 2022-07-27 오후 6.20.39

That userManager is declared after page 136.
In short, the order of this book is messed up.
Is this forum and book not maintained by anyone?

Thank you for your great interest.
Also, you are very responsible.

I gave up reading this book after this problem.
I could tell the quality of the book just by looking at these small details.

Hi @usinuniverse, really sorry for not replying earlier, but got my email notifications messed up due to a mistake I made in my gmail filter. I really appreciate you reporting this, and I understand if you feel frustrated for the lack of answers — 100% my fault.

I’ll fix this.