C++繼承

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; 

} 

編譯器返回錯誤：

main.cpp中：在成員函數 '虛擬無效CThirdLevel ::則PushBack（T）'：

main.cpp中： 32:37：錯誤：'數據'未在此範圍內聲明

問題在哪裏？有可能使用這個繼承嗎？

Answer 1

問題出在CThirdLevel。該字段data無法從CSecondLevel解決。你可以通過改變

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

解決這

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

Answer 2

正如馬克建議，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); }