Are there any methods like isDestroyed or isDisposed to detect whether some object is destroyed or not?

[Dan Olson via Digitalmars-d-learn]

"Marc "Schütz\"" <schuetzm at gmx.net> writes:

> On Saturday, 13 December 2014 at 21:20:43 UTC, Andrey Derzhavin wrote:
>>>
>>> import std.stdio;
>>>
>>> class ObjectAType {
>>>    bool ok;
>>>    this() {ok = true;}
>>> }
>>>
>>> void main()
>>> {
>>>    auto a = new ObjectAType;
>>>    assert(a.ok);
>>>    destroy(a);
>>>    assert(!a.ok);  // a has been destroyed.
>>> }
>>>
>>
>> This method of detection of collected objects is what I needed.
>> Thanks to everybody for your advise.
>
> Be careful - the memory could still have been reused. For example:
>
>     assert(a.ok);
>     destroy(a);
>     // ... lots of code, maybe multi-threaded ...
>     assert(!a.ok);    // can fail
>
> If between `destroy()` and the second `assert()`, the memory of the
> object is collected, a new object (of the same or different type) can
> have been placed there. You will then read an arbitrary piece of data
> from that new object, which may or may not evaluate to `true`.

In this case the object cannot be collected by gc because there is still
a good reference to it (variable 'a').  I agree if delete was used
instead of destroy that is would be unsafe.
--
dano