On 12/13/14 2:03 AM, Andrey Derzhavin wrote:
Hello!
We have object, for example, objA.
ObjectAType objA = new ObjectAType(...);
// we have a many references to objA
void someFunction1(...)
{
// destroying the objA
destroy(one_of_the_refToObjA);
//........
}
void someFunction2(....)
{
// "segmentation fault" if the objA is destroyed
another_refToObjA.method1();
// I need a safe way (without using signals) to detect whether object
// destroyed or not, like this
// if (!isDestroyed(another_refToObjA))
// another_refToObjA.method1();
}
// call functions
someFunction1(..);
// ..... some other operations...
// the objectA (objA) is destroyed, but debugger shows us a not null
reference
// to that objA. However, when we try to call some methods of objectA or
// try to use it's variables we get a "segmentation fault" error (in
// someFunction2, when objA is destroyed).
someFunction2(...);
Yes, you can tell if the typeinfo pointer is null, this is how the
runtime does it.
Unfortunately, typeid(objA) uses the pointer to look up the most derived
type and results in a segfault.
You can use the knowledge of the object layout (the typeinfo pointer is
the first item in the memory block) to ascertain whether it's null or
not, it's what the runtime does:
bool isDestroyed(Object o)
{
return o is null || *(cast(void **)o) is null;
}
Although, I highly recommend not doing this. Instead of destroying an
object, leave the object live and dispose of it using some other method
(e.g. close, dispose, etc.). Then let the GC clean up the memory later
when nothing refers to it.
-Steve
