Simon TRENY wrote:
grauzone Wrote:
Simon TRENY wrote:
Hi there!
I'm quite new at D and I'm still just playing with it, but there is a thing
that I find currently missing. Sometimes, I'd like to be able to return a
struct by reference and not by value. For example, in the following example:
struct Position {
float x;
float y;
}
class Object {
private Position m_position;
public Position position() {
return m_position;
}
}
I'd like to be able to write things like this: myObject.position.x = 43 to actually
change the position of the object. But right now, since "position" is a struct,
it is returned by value and not by reference, and then the previous instruction won't
change the position of the object, but it will work on a copy of the position field.
Here is the solutions that I can see to this problem:
- Returning a pointer to the position: "public Position *position() { ... }",
but I'd like to keep my code as free from pointers as possible.
- Make "Position" a class and not a struct. That could be a solution, but then, when
I'll do things like "Position pos = object.position; pos.x = 43;", it will effectively
change the position of the object, which I wouldn't like with this syntax.
Actually, I'd like to be able to do a thing like this:
public ref Position position() {
return m_position;
}
which would be the equivalent form to passing structs by reference in a
parameter.
Is there a way to do this in D?
Yes. Make the variable public.
class Object {
Position position;
}
This code is even simpler than your's above. Incredible, isn't it?
Ok, but then, what if I'd like to make the variable "read-only"? i.e.
preventing the user from writing things like this:
myObject.position = pos2;
Then you write a getter that simply returns the field by value.
The D compiler will (hopefully) inline the getter function, so there
shouldn't be a disadvantage in performance.
Note: I think D2.0 wants to introduce ref-returns at some point in the
future.
Regards,
Simon
