我已经问了一个与私有析构函数相关的问题（使用使析构函数成为私有），但我以下面的问题结束，但我仍然不明白确切的答案。
问题：
当我创建具有私有析构函数的类对象时，为什么会调用私有析构函数？但不是当我创建一个普通对象时。
案例一
// myclass.h
#include <iostream>
class MyClass {
public:
static MyClass& GetInstance();
void Display();
private:
MyClass();
virtual ~MyClass();
};
MyClass::MyClass() {
std::cout << "Constructor " << std::endl;
}
MyClass::~MyClass() {
std::cout << "Destructor" << std::endl;
}
MyClass& MyClass::GetInstance() {
static MyClass _instance;
return _instance;
}
void MyClass::Display() {
std::cout << "Hello" << std::endl;
}
// main.cpp
#include "myclass.h"
#include <iostream>
int main() {
MyClass::GetInstance().Display(); //case1
std::cout << "main finished!" << std::endl;
return 0;
}
// output
Constructor
main finished
Destructor.
案例二
// myclass.h
#include <iostream>
class MyClass {
public:
void Display();
MyClass();
virtual ~MyClass();
};
MyClass::MyClass() {
std::cout << "Constructor " << std::endl;
}
MyClass::~MyClass() {
std::cout << "Destructor" << std::endl;
}
MyClass& MyClass::GetInstance() {
static MyClass _instance;
return _instance;
}
void MyClass::Display() {
std::cout << "Hello" << std::endl;
}
// main.cpp
#include "myclass.h"
#include <iostream>
int main() {
MyClass testObj;
std::cout << "main finished!" << std::endl;
return 0;
}
// Error
1>e:\programs\cpp_test\src\main.cpp(38): error C2248: 'MyClass::MyClass' : cannot access private member declared in class 'MyClass'
1> e:\programs\cpp_test\static_single_test.h(11) : see declaration of 'MyClass::MyClass'
1> e:\programs\cpp_test\static_single_test.h(6) : see declaration of 'MyClass'
1>e:\programs\cpp_test\src\main.cpp(38): error C2248: 'MyClass::~MyClass' : cannot access private member declared in class 'MyClass'
1> e:\programs\cpp_test\static_single_test.h(12) : see declaration of 'MyClass::~MyClass
编辑
我已经知道，当我们“仅需要基于堆的对象”时，需要将析构函数设为保护/私有。