How to declare a virtual member (not a function) in a class

[Petar]

On Tuesday, 18 February 2020 at 12:37:45 UTC, Adnan wrote:
> I have a base class that has a couple of constant member 
> variables. These variables are abstract, they will only get 
> defined when the derived class gets constructed.
>
> class Person {
>     const string name;
>     const int id;
> }
>
> class Male : Person {
>     this(string name = "Unnamed Male") {
>         static int nextID = 0;
>         this.id = nextID++;
>         this.name = name;
>     }
> }
>
> The compiler restricts me from assigning those two functions. 
> How can I get around this?

`const` members must be initialized by the same class that 
declares them. What you could do is have the abstract Person 
class declare a constructor (which would initialize the `const` 
members) and call it from derived class (such as `Male`) 
constructors by the `super(arg1, arg2)` syntax.

Alternatively, you could define `abstract` accessor functions in 
the base class and have the derived classes implement them. In D 
you can use the same syntax to call functions as if they were 
fields. (Before you had to put the @property attribute on such 
functions, but for the most part it is not necessary now.)