The first C++ compiler (“C with classes”) would actually generate C code, so that’s definitely doable. Basically, your base class is a struct; derived structs must include the base struct at the first position, so that a pointer to the “derived” struct will also be a valid pointer to the base struct. typedef struct { … Read more
Look at Activator.CreateInstance(). myObject = (MyAbstractClass)Activator.CreateInstance(“AssemblyName”, “TypeName”); or var type = Type.GetType(“MyFullyQualifiedTypeName”); var myObject = (MyAbstractClass)Activator.CreateInstance(type);
You need to use virtual keyword abstract class Base { // use virtual keyword public virtual int x { get { throw new NotImplementedException(); } } } or define an abstract property: abstract class Base { // use abstract keyword public abstract int x { get; } } and use override keyword when in the … Read more
What is the monomorphism restriction? The monomorphism restriction as stated by the Haskell wiki is: a counter-intuitive rule in Haskell type inference. If you forget to provide a type signature, sometimes this rule will fill the free type variables with specific types using “type defaulting” rules. What this means is that, in some circumstances, if … Read more
Polymorphism allows the expression of some sort of contract, with potentially many types implementing that contract (whether through class inheritance or not) in different ways, each according to their own purpose. Code using that contract should not(*) have to care about which implementation is involved, only that the contract will be obeyed. (*) In the … Read more
The instanceof keyword, as described by the other answers, is usually what you would want. Keep in mind that instanceof will return true for superclasses as well. If you want to see if an object is a direct instance of a class, you could compare the class. You can get the class object of an … Read more
I would suggest: Using only one URI per resource Differentiating between animals solely at the attribute level Setting up multiple URIs to the same resource is never a good idea because it can cause confusion and unexpected side effects. Given that, your single URI should be based on a generic scheme like /animals. The next … Read more
An interface describes what one needs to know in order to interact in a given situation in code. Once you extend the interface with “your entire type hierarchy”, your interface “surface area” becomes huge, which makes reasoning about it harder. As an example, your “poke adjacent oranges” means that I, as a 3rd party, cannot … Read more
You might be interested in this entry from Steve Yegge’s Amazon blog: “when polymorphism fails”. Essentially he’s addressing cases like this, when polymorphism causes more trouble than it solves. The issue is that to use polymorphism you have to make the logic of “handle” part of each ‘switching’ class – i.e. Integer etc. in this … Read more
This is a bit late but I had to do exactly the same thing today. So, based on my research and when using gson-2.0 you really don’t want to use the registerTypeHierarchyAdapter method, but rather the more mundane registerTypeAdapter. And you certainly don’t need to do instanceofs or write adapters for the derived classes: just … Read more