where to use Private Variables

private Variables in Flutter:

• used when we just want certain instance variables or functions visible outside of that class
• https://softwareengineering.stackexchange.com/a/143739

So, as to when you should make things private: I'd say MAKE EVERYTHING PRIVATE BY DEFAULT, and then expose only those parts that absolutely have to be public. The more you can make private, the better.

When are Getters and Setters Justified?

• https://softwareengineering.stackexchange.com/questions/21802/when-are-getters-and-setters-justified