et we forward the key input information to Evaluators. Evaluators keep current state of key input and does some operation on the current text view.
When a evaluator evaluate key input but still need some key input to complete the operation it will return next evaluator as its return value.

<h2>Xcode internal classes</h2>
You can find internal classes or methods <a href="https://github.com/probablycorey/xcode-class-dump/tree/master/docs">here</a>
This is help to understand its internal and functions.
Especi