destructor

问题 Looking for a construct in javascript which works like the destructor in stackbased or local object in c++, e.g. #include <stdio.h> class M { public: int cnt; M() {cnt=0;} void inc() {cnt++;} ~M() {printf ("Count is %d\n", cnt);} }; ... {M m; ... m.inc (); ... m.inc (); } // here the destructor of m will printf "Count is 2"); so this means I am looking for a construct which does an action when its scope is ending (when it "goes out of scope"). It should be robust in the way that it does not

问题 I heard that empty destructor doesn't do anything and calling it doesn't remove the object. But in the code: #include <iostream> #include <set> class a { public: ~a() {} std::set <int> myset; }; int main() { a object; object.myset.insert(55); object.~a(); object.myset.insert(20); std::cout << object.myset.size(); } I get: " * glibc detected * /.app: double free or corruption (fasttop):" and then "ABORT". If it matters I have c++11 flag enabled. So what does empty constructor actually do? It

问题 I use Borland C++ Builder. And i had o problem #include <Classes.hpp> class TMyObject : public TObject { __fastcall TMyObject(); __fastcall ~TMyObject();//I would like to inherite my destructor from TObject }; __fastcall TMyObject::TMyObject() : TObject()//it will inherited my constructor from TObject { } And for that new destructor that will inherite ~TObject ? __fastcall TMyObject::~TMyObject????????????? 回答1: This can be solved at TObject 's level. Its destructor has to be virtual:

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 5 years ago . Is it good practice (and is it possible) to create an abstract class using only a pure virtual destructor in the parent class? Here's a sample class AbstractBase { public: AbstractBase () {} virtual ~AbstractBase () = 0; }; class Derived : public AbstractBase { public: Derived() {} virtual ~Derived

问题 I have the following: template <typename X> struct A { typedef X _X; }; template <typename Y> struct B { // Y is struct A typename Y::_X x; void call_destructor () { x.~Y::_X(); // This doesn't work x.Y::~_X(); // This as well } }; which doesn't compile, saying that qualified type does not match destructor name Using the keyword typename before the call also does not work. However, the following does compile: template <typename Y> struct B { typename Y::_X x; typedef typename Y::_X __X; void

问题 I'm trying to write a unit test that detects an invalid use of the lock() feature of my class. In order to do so, I want to use the destructor and throw an exception from there. Unfortunately, instead of catching the exception, g++ decides to call std::terminate(). There is a very simplified version of the class: class A { public: A() : f_lock(0) {} ~A() { if(f_lock) throw my_exception("still locked"); } lock() { ++f_lock; } unlock() { --f_lock; } private: int f_lock; }; There is a valid test

问题 recently in a job interview I was asked about the problem of leaking memory in derived classes when the base class's destructor is not declared virtual. I wrote a small test to confirm my answer, but I found something interesting. Obviously, if you create a Derived object via new but store its pointer as a Base* , the derived object's destructor won't be called, if the pointer is deleted (so much for my answer to the question). I thought whether the derived class's destructor is virtual or

问题 When I'm inside a destructor is it possible that some other thread will start executing object's member function? How to deal with this situation? 回答1: C++ has no intrinsic protection against using an object after it's been deleting - forget about race conditions - another thread could use your object after it's been completely deleted. Either: Make sure only one place in the code owns the object, and it's responsible for deleting when no-one is using the object. Make the object reference

问题 I am making a simple class that contains a StreamWrite class Logger { private StreamWriter sw; private DateTime LastTime; public Logger(string filename) { LastTime = DateTime.Now; sw = new StreamWriter(filename); } public void Write(string s) { sw.WriteLine((DateTime.Now-LastTime).Ticks/10000+":"+ s); LastTime = DateTime.Now; } public void Flush() { sw.Flush(); } ~Logger() { sw.Close();//Raises Exception! } } But when I close this StreamWriter in the destructor, it raises an exception that

问题 I need to create a service which will maintain a WCF session. In the constructor I read in data from the DB and when the session ends I have to save it back. If I understand correctly the session ends when I call Close() on the Client (My client ServiceClient was created with SvcUtil.exe). When I test it I see that it is sometimes called after approx. 10 minutes, sometimes after 20 minutes and sometimes not at all. So when is the destructor called? Service [ServiceBehavior(InstanceContextMode