I smell a code smell here. It is my opinion that you should only inherit a base class if you’re implementing all of the functionality of that base class. What you’re doing doesn’t really represent object oriented principles properly. Thus, if you want to inherit from your base, you should be implementing Name, otherwise you’ve … Read more
No. A reference to a derived class must actually refer to an instance of the derived class (or null). Otherwise how would you expect it to behave? For example: object o = new object(); string s = (string) o; int i = s.Length; // What can this sensibly do? If you want to be able … Read more
This is simply how C# is going to work. The constructors for each type in the type hierarchy will be called in the order of Most Base -> Most Derived. So in your particular instance, it calls Person(), and then Customer() in the constructor orders. The reason why you need to sometimes use the base … Read more
There are examples in the Framework with the Base suffix, e.g. System.Configuration.Provider.ProviderBase, System.Web.SessionState.SessionStateStoreProviderBase. But by no means all abstract base classes in the Framework follow this convention (e.g. System.Data.Common.DbParameter, System.Data.Common.DbCommand). Personally I would avoid using the suffix unless I wanted to emphasize the fact that it’s an abstract class and felt that otherwise users of … Read more
The destructor of A will run when its lifetime is over. If you want its memory to be freed and the destructor run, you have to delete it if it was allocated on the heap. If it was allocated on the stack this happens automatically (i.e. when it goes out of scope; see RAII). If … Read more
Let’s take your example of a Dog and a Cat class, and let’s illustrate using C#: Both a dog and a cat are animals, specifically, quadruped mammals (animals are waaay too general). Let us assume that you have an abstract class Mammal, for both of them: public abstract class Mammal This base class will probably … Read more
Use a Metaclass I would recommend Method #2, but you’re better off using a metaclass than a base class. Here is a sample implementation: class Singleton(type): _instances = {} def __call__(cls, *args, **kwargs): if cls not in cls._instances: cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs) return cls._instances[cls] class Logger(object): __metaclass__ = Singleton Or in Python3 class Logger(metaclass=Singleton): … Read more