Stage 9.13: Sharing Access
RefCell is a container data structure commonly held by smart pointers that takes in
data and lets us borrow mutable and immutable references to what's inside. It prevents borrowing
from being abused by enforcing Rust's memory safety rules at runtime when you ask to borrow the data
within:
Only one mutable reference OR multiple immutable references, but not both!
If you violate these rules RefCell will panic.
Further information: