Reference type demonstration
class C { struct Agg { static int dtorCount; int x = 10; ~this() { dtorCount++; } } static int dtorCount; string s = "S"; Agg a; ~this() { dtorCount++; } } C c = new C(); assert(c.dtorCount == 0); // destructor not yet called assert(c.s == "S"); // initial state `c.s` is `"S"` assert(c.a.dtorCount == 0); // destructor not yet called assert(c.a.x == 10); // initial state `c.a.x` is `10` c.s = "T"; c.a.x = 30; assert(c.s == "T"); // `c.s` is `"T"` destroy(c); assert(c.dtorCount == 1); // `c`'s destructor was called assert(c.s == "S"); // `c.s` is back to its inital state, `"S"` assert(c.a.dtorCount == 1); // `c.a`'s destructor was called assert(c.a.x == 10); // `c.a.x` is back to its inital state, `10`
C++ classes work too
extern (C++) class CPP { struct Agg { __gshared int dtorCount; int x = 10; ~this() { dtorCount++; } } __gshared int dtorCount; string s = "S"; Agg a; ~this() { dtorCount++; } } CPP cpp = new CPP(); assert(cpp.dtorCount == 0); // destructor not yet called assert(cpp.s == "S"); // initial state `cpp.s` is `"S"` assert(cpp.a.dtorCount == 0); // destructor not yet called assert(cpp.a.x == 10); // initial state `cpp.a.x` is `10` cpp.s = "T"; cpp.a.x = 30; assert(cpp.s == "T"); // `cpp.s` is `"T"` destroy!false(cpp); // destroy without initialization assert(cpp.dtorCount == 1); // `cpp`'s destructor was called assert(cpp.s == "T"); // `cpp.s` is not initialized assert(cpp.a.dtorCount == 1); // `cpp.a`'s destructor was called assert(cpp.a.x == 30); // `cpp.a.x` is not initialized destroy(cpp); assert(cpp.dtorCount == 2); // `cpp`'s destructor was called again assert(cpp.s == "S"); // `cpp.s` is back to its inital state, `"S"` assert(cpp.a.dtorCount == 2); // `cpp.a`'s destructor was called again assert(cpp.a.x == 10); // `cpp.a.x` is back to its inital state, `10`
Value type demonstration
int i; assert(i == 0); // `i`'s initial state is `0` i = 1; assert(i == 1); // `i` changed to `1` destroy!false(i); assert(i == 1); // `i` was not initialized destroy(i); assert(i == 0); // `i` is back to its initial state `0`
Nested struct type
int dtorCount; struct A { int i; ~this() { dtorCount++; // capture local variable } } A a = A(5); destroy!false(a); assert(dtorCount == 1); assert(a.i == 5); destroy(a); assert(dtorCount == 2); assert(a.i == 0); // the context pointer is now null // restore it so the dtor can run import core.lifetime : emplace; emplace(&a, A(0)); // dtor also called here
Destroys the given object and optionally resets to initial state. It's used to destroy an object, calling its destructor or finalizer so it no longer references any other objects. It does not initiate a GC cycle or free any GC memory. If initialize is supplied false, the object is considered invalid after destruction, and should not be referenced.