When To Use Interfaces An interface allows somebody to start from scratch to implement your interface or implement your interface in some other code whose original or primary purpose was quite different from your interface. To them, your interface is only incidental, something that have to add on to the their code to be able … Read more
In Framework Design Guidelines p 174 states: Avoid naming base classes with a “Base” suffix if the class is intended for use in public APIs. Also : http://blogs.msdn.com/kcwalina/archive/2005/12/16/BaseSuffix.aspx
I assume that with interface you mean a C++ class with only pure virtual methods (i.e. without any code), instead with abstract class you mean a C++ class with virtual methods that can be overridden, and some code, but at least one pure virtual method that makes the class not instantiable. e.g.: class MyInterface { … Read more
When writing a C++ class, it’s appropriate to think about whether it’s going to be A Value Type Copy by value, identity is never important. It’s appropriate for it to be a key in a std::map. Example, a “string” class, or a “date” class, or a “complex number” class. To “copy” instances of such a … Read more
Python 3.3+ from abc import ABCMeta, abstractmethod class A(metaclass=ABCMeta): def __init__(self): # … pass @property @abstractmethod def a(self): pass @abstractmethod def b(self): pass class B(A): a = 1 def b(self): pass Failure to declare a or b in the derived class B will raise a TypeError such as: TypeError: Can’t instantiate abstract class B with … Read more
Without the designers of java.lang.Object telling us, we have to base our answers on opinion. There’s a few questions which can be asked which may help clear it up. Would any of the methods of Object benefit from being abstract? It could be argued that some of the methods would benefit from this. Take hashCode() … Read more
Just to chime in late here, I think that there’s no reason to stop somebody from instantiating the abstract class, especially because they can add methods to it on the fly. Duck-typing languages, like Ruby, use the presence/absence or behavior of methods at runtime to determine whether they should be called or not. Therefore your … Read more
That’s because if a class is abstract, then by definition you are required to create subclasses of it to instantiate. The subclasses will be required (by the compiler) to implement any interface methods that the abstract class left out. Following your example code, try making a subclass of AbstractThing without implementing the m2 method and … Read more
Update: C# 8.0 New Feature: Beginning with C# 8.0, an interface may define a default implementation for members, including properties. Defining a default implementation for a property in an interface is rare because interfaces may not define instance data fields. The advantages of an abstract class are: Ability to specify default implementations of methods Added … Read more
An abstract class is a class that contains at least one abstract method, which is a method without any actual code in it, just the name and the parameters, and that has been marked as “abstract”. The purpose of this is to provide a kind of template to inherit from and to force the inheriting … Read more