On Sunday, 3 February 2013 at 02:55:44 UTC, Zach the Mystic wrote:
On Saturday, 2 February 2013 at 20:30:26 UTC, Era Scarecrow
wrote:
Yes, it should be callable that way since it knows where a is
at. However I would think a nested struct is more a
implementation detail.
I think this belittles just how important that implementation
detail really is. Without a good design, the thing could be
prohibitively difficult to implement.
From what I understand generally, good encapsulation is a
difficult design problem. I don't think you're alone.
In short, nested structs would only be accessible (and
passable) inside the struct that made it. Meaning that most
likely the methods that work with it, and the struct itself
should be private.
Well, if you want access to a struct from outside, save
yourself the time and put it outside to begin with. A nested
struct of course is directly related to the entity it finds
itself in. My pet metaphor is struct Dog containing struct
Tail. It would definitely be illogical to put the Tail outside
the Dog.
Agreed 100%, Although a second (instance of) Dog may want to
come about and them sniff tails. That's outside access, but it's
still within the limits of the Dogs. In those cases a context
pointer could be acceptable as long as it's ensuring the data
exists (and can't return it from the function); But overwriting
one instance with a different context pointer of another could
have very curious side effects depending on design.
struct Dog {
int id;
struct Tail {
string colorOf = "Black"; //just data.
int getId() { return id; }
}
Tail tail;
void func(ref Dog rhs) {
//tail2 retains context pointer to rhs.
Tail tail2 = rhs.tail;
writeln(tail.getId()); //5
writeln(tail2.getId()); //10
}
}
Dog dog1 = Dog(5);
Dog dog2 = Dog(10); dog2.tail.colorOf = "White";
dog1.func(dog2);
//context pointer of d2 thrown away after copy,
//unless opAssign declared and does something.
dog1.tail = dog2.tail;
assert(d1.id == 5); //untouched
assert(d1.tail.colorOf == "White");
At which case the tail if it's allowed to be copied should be
related but not strictly required to be updated or relied on Dog
for behavior.
Guess it takes a few rules and experiments to find the right
balance of accessibility vs reliability vs flexibility.
