Re: How to declare a virtual member (not a function) in a class
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.)
Re: How to declare a virtual member (not a function) in a class
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 can only be set in the constructor of the type that
defines them. To set them in a subclass, forward the values to
the superclass' constructor:
class Person {
const string name;
const int id;
protected this(string _name, int _id) {
id = _id;
name = _name;
}
}
class Male : Person {
this(string name = "Unnamed Male") {
static int nextID = 0;
super(name, nextID++);
}
}
--
Simen
How to declare a virtual member (not a function) in a class
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?
