Avoid protected data

All data in a base class should be private; do not use protected data. --Riel's Heuristic 5.3, Arthur Riel 1996

• data - The fields defined within a class
• private - To restrict accessibility to within an instance of a class
• protected - To restrict accessibility to within an instance of a class, and to instances of inheriting classes

Description

Riel's Heuristic #5.3 demands that access to a class's fields should be restricted to instances of that class. Inheriting classes should access these fields via accessor methods only. By restricting a subclass's field accesses in this way, a designer is free to change the manner in which the data is stored within the base class, with minimal effect on subclasses.

See Also

• Information hiding
• Minimize accesses to variables
• Getters and setters
• Riel's heuristics
• Design maxims

Conflicts with

Object encapsulation. See:Encapsulation boundary