On Tuesday, 17 January 2017 at 15:59:26 UTC, Andrei Alexandrescu
wrote:
On 1/17/17 12:08 PM, Mark wrote:
On Tuesday, 17 January 2017 at 09:17:56 UTC, Andrei
Alexandrescu wrote:
On 1/17/17 9:32 AM, Eugene Wissner wrote:
Ah, well thanks. I don't think it makes much sense since it
would be
easier to write a complete setter if the user needs extra
checks.
Accessors are there only for the generation of the standard
methods,
that just get or set some object property.
Hmmm... that's a bit of a bummer because it helps only the
degenerate
case (accessors are there as placeholders for future
extensions, and
otherwise offer no protection whatsoever compared to a public
value).
The question would be then what would be use cases for the
accessors.
Predicated setters are not just a random thing one might want
out of
many possibilities, it's a frequent pattern. -- Andrei
Given that D supports class invariants, is there a real need
for
predicated setters?
The invariant is evaluated after the setter has taken place,
i.e. after the object has been corrupted. The setter guard
prevents corruption from happening. -- Andrei
I see. Is there a way to call invariant() of a class/struct
directly? That would obviate the need for a particular predicate
(copy the class state, run the setter, check if invariants are
satisfied and restore previous state if they aren't).
