In design, you want the base class class A to present only an interface for its derived classes. This means, you don’t want anyone to actually instantiate an object of the base class. You only want to upcast to it (implicit upcasting, which gives you polymorphic behavior), so that its interface can be used. This … Read more
The problem is that you’re trying to use the T from SqlReaderBase as the type argument for MapperBase – but you don’t have any constraints on that T. Try changing your SqlReaderBase declaration to this: public abstract class SqlReaderBase<T> : ConnectionProvider where T : new() Here’s a shorter example which demonstrates the same issue: class … Read more
I finally solved it! // GSON GsonBuilder gsonBilder = new GsonBuilder(); gsonBilder.registerTypeAdapter(Conteudo.class, new InterfaceAdapter<Conteudo>()); gsonBilder.setPrettyPrinting(); Gson gson =gsonBilder.create(); String str2send = gson.toJson(message); Mensagem msg_recv = gson.fromJson(str2send,Mensagem.class); Note that: “registerTypeAdapter(AbstractClass.class, new InterfaceAdapter());” by AbstractClass.class i mean the class that you are implementing in my case it was Conteúdo that could be ConteudoTweet or ConteudoUserSystem and so … Read more
Hence does it mean that even if a constructor completes running without any exception, there is no guarantee whether an object is created? Simply speaking, a constructor does not create an object. It just initializes the state of the object. It’s the new operator which creates the object. Now, let’s understand this in little detail. … Read more
Interfaces allow you to use classes in different hierarchies, polymorphically. For example, say you have the following interface: public interface Movable { void move(); } Any number of classes, across class hierarchies could implement Movable in their own specific way, yet still be used by some caller in a uniform way. So if you have … Read more
An answer to your first question: The virtual destructor in your dll is called – the information about its location is embedded in your object (in the vtable). In the case of memory deallocation it depends how disciplined the users of your IBase are. If they know they have to call Release() and consider that … Read more
You can return an abstract class pointer – assuming B is a concrete class derived from abstract class A: A * f() { return new B; } or a reference: A & f() { static B b; return b; } or a smart pointer: std::unique_ptr<A> f() { return std::make_unique<B>(…); }
Ok, I’ve just learned something. A pure virtual function must be declared as follows: class Abstract { public: virtual void pure_virtual() = 0; }; It may have a body, although it is illegal to include it at the point of declaration. This means that to have a body the pure virtual function must be defined … Read more
Short Answer: No. Long Answer: It is not the base class or the number of ancestors a class has in its hierarchy that affects it speed. The only thing is the cost of a method call. A non virtual method call has a cost (but can be inlined) A virtual method call has a slightly … Read more
The implements keyword treats the A class as an interface, that means C has to implement all the methods defined in A, no matter if they have an implementation or not in A. Also there are no calls to super methods in C. extends behaves more like what you’d expect from the keyword. You have … Read more