notes on "Clean Code - Objects and Data structures" chapter

• Hiding implementation is about making abstractions and not putting layers of functions (like numerous getters and setters).
• “Objects hide the data behind abstractions and expose functions that operate on that data.”
• “Data structures just expose their data and have no meaningful functions.”
• Procedural code makes it easy to add new functions without changing the existing data structures. OO code, on the other hand, makes it easy to add new classes without changing existing functions.
• “Mature programmers know that the idea that everything is an object is a myth.”
• The Law of Demeter
  Method f of class C should only call the methods of these:
  • C (itself)
  • An object created by f
  • An object passed as an argument to f
  • An object held in an instance variable of C
• The method should not invoke methods on objects that are returned by the allowed functions!
• If the things which are accessed within a method are data structures with no behavior the Law of Demeter do not apply.
• Avoid creating hybrids (half object - half data structures) - classes which have meaningful methods and expose internal structure via getters/setters.
• Refactoring note: Try to identify what exposed data is used for -> maybe it is possible to extract a method and move it to the exposing class?