如何利用c++编写不能被继承、但可以在类外定义对象的类

 1 #include <iostream>
 2 #include<string>
 3 #include<map>
 4 #include<vector>
 5 #include"thread_pool.h"
 6 
 7 
 8 using namespace std;
 9 template<class T>
10 class base{
11     friend T;/// friend class
12 private:
13     base(){}
14     ~base(){}
15 };
16 
17 class derived : public virtual base<derived>
18 {
19 public:
20     derived(){}
21     void show(){
22         cout<<"can be instanced,but can not be inherited"<<endl;
23     }
24     ~derived(){}
25 };
26 
27 class dderived : public derived{
28 public:
29     dderived(){}
30     ~dderived(){}
31 };
32 
33 
34 
35 int main()
36 {
37     cout << "Hello world!" << endl;
38     derived d;
39     d.show();
40     return 0;
41 }

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