c++ - 模板对象的 C++ 继承（G++ 编译器）

Question

#include <cstdlib>
#include <vector>
#include <iostream>

using namespace std;

class CFirstLevel {
 public:
    CFirstLevel (const string & _name): name (_name) {}
    // ...

 protected:

    string name;

};

template <typename T>
class CSecondLevel: public CFirstLevel {
 public:

    CSecondLevel (const string & _name): CFirstLevel (_name) {}

    virtual void PushBack (T) = 0;
    virtual void Print    (int I) {cout << data [I] << endl;}
    // ...

 protected:
    vector<T> data; 
};

template <typename A>
class CThirdLevel: public CSecondLevel<A> {
 public:
    CThirdLevel (const string & _name): CSecondLevel<A> (_name) {}

    virtual void PushBack (A _value) {data.push_back (_value);}

};


int main ( void ) {

    CThirdLevel<int> * pointer = new CThirdLevel<int> ("third");
    pointer -> PushBack (111);

    pointer -> Print (0);

    return 0;

}

编译器返回错误：

main.cpp：在成员函数'virtual void CThirdLevel::PushBack(T)'中：

main.cpp:32:37：错误：“数据”未在此范围内声明

哪里有问题？是否可以使用这种继承？

Answer 1

问题出在CThirdLevel. data无法从 解析该字段CSecondLevel。您可以通过更改来解决此问题

virtual void PushBack (A _value) {data.push_back (_value);}

到

virtual void PushBack (A _value) {CSecondLevel<A>::data.push_back (_value);}

Answer 2

正如马克建议的那样，使用

virtual void PushBack (A _value) { CSecondLevel<A>::data.push_back (_value); }

或者，你可以做

virtual void PushBack (A _value) { this->data.push_back (_value); }