Considering object encapsulation, should getters return an immutable property?

Question

When a getter returns a property, such as returning a List of other related objects, should that list and it\'s objects be immutable to prevent code outside of

Answer 1

Your first imperative should be to follow the Law of Demeter or ‘Tell don't ask’; tell the object instance what to do e.g.

contact.print( printer ) ;  // or
contact.show( new Dialog() ) ; // or
contactList.findByName( searchName ).print( printer ) ;

Object-oriented code tells objects to do things. Procedural code gets information then acts on that information. Asking an object to reveal the details of its internals breaks encapsulation, it is procedural code, not sound OO programming and as Will has already said it is a flawed design.

If you follow the Law of Demeter approach any change in the state of an object occurs through its defined interface, therefore side-effects are known and controlled. Your problem goes away.