class variable initialization

[Vijay Nayar]

On Saturday, 15 April 2023 at 14:05:17 UTC, NonNull wrote:
> I want a way to default initialize a class variable to a 
> default object (e.g. by wrapping it in a struct, because 
> initialization to null cannot be changed directly). Such a 
> default object is of course not available at compile time which 
> seems to make this impossible. Can this be done in some way?

Assuming you want a default object that is unique per class 
instance rather than shared among all instances of the same 
class, then I think the constructor might be where you want to 
initialize such a member.

E.g.
```
class Var {
   int val;
   this(int val) {
     this.val = val;
   }
}

class MyClass {
   Var var;

   this() {
     var = new Var(3);
   }
}
```

I believe if you do initialization at the class declaration 
level, then every instance of the class shares the same instance, 
e.g.:

```
class Var {}

class MyClass {
   Var var = new Var();
}

void main() {
   MyClass c1 = new MyClass();
   MyClass c2 = new MyClass();
   assert(c1.var is c2.var);
}
```