分析构造函数和析构函数调用次序

发布网友发布时间：2022-05-25 14:53

共2个回答

热心网友时间：2023-11-06 00:08

好无聊的问题，自己随便写点测试代码也有结果了。
原则并不复杂，构造类时，先按继承的顺序构造各父类，完成后，再按成员定义的顺序构造各成员。析构是反序。

热心网友时间：2023-11-06 00:09

（1）
#include <iostream>
using namespace std;
class A
{
public:
A()
{
cout <<"constructing A"<<endl;
}
~A()
{
cout <<"Destructing A"<<endl;
}
};
class C
{
public:
C()
{
cout <<"constructing C"<<endl;
}
~C()
{
cout <<"Destructing C"<<endl;
}
};
class B:public A
{
public:
C c;
B()
{
cout <<"constructing B"<<endl;
}
~B()
{
cout <<"Destructing B"<<endl;
}
};
class D: public B
{
public:
D(){
cout <<"constructing D"<<endl;
}
~D(){
cout <<"Destructing D"<<endl;
}
};
int main()
{
D d;
return 0;
}
输出：
constructing A
constructing C
constructing B
constructing D
Destructing D
Destructing B
Destructing C
Destructing A
（2）
#include <iostream>
using namespace std;
class A
{
public:
A()
{
cout <<"constructing A"<<endl;
}
~A()
{
cout <<"Destructing A"<<endl;
}
};
class C:public A
{
public:
C()
{
cout <<"constructing C"<<endl;
}
~C()
{
cout <<"Destructing C"<<endl;
}
};
class B:public A
{
public:
C c;
B()
{
cout <<"constructing B"<<endl;
}
~B()
{
cout <<"Destructing B"<<endl;
}
};
class D: public B
{
public:
D(){
cout <<"constructing D"<<endl;
}
~D(){
cout <<"Destructing D"<<endl;
}
};
输出：
constructing A
constructing A
constructing C
constructing B
constructing D
Destructing D
Destructing B
Destructing C
Destructing A
Destructing A
（3）
#include <iostream>
using namespace std;
class A
{
public:
A()
{
cout <<"constructing A"<<endl;
}
~A()
{
cout <<"Destructing A"<<endl;
}
};
class C:virtual public A
{
public:
C()
{
cout <<"constructing C"<<endl;
}
~C()
{
cout <<"Destructing C"<<endl;
}
};
class B:virtual public A
{
public:
C c;
B()
{
cout <<"constructing B"<<endl;
}
~B()
{
cout <<"Destructing B"<<endl;
}
};
class D: public B
{
public:
D(){
cout <<"constructing D"<<endl;
}
~D(){
cout <<"Destructing D"<<endl;
}
};
输出：
constructing A
constructing A
constructing C
constructing B
constructing D
Destructing D
Destructing B
Destructing C
Destructing A
Destructing A