Question

我目前正在尝试编写一个包含虚拟方法和朋友的模板类。我想在我的测试功能中调用它们。我的代码是：

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <iterator>
#include <array>
using namespace std;
template <class T> class ProcessorBase;
template <class T> ostream& operator<<(ostream &, const ProcessorBase<T> &);
template<class T>
class ProcessorBase
{
protected:
vector<T> v;
public:
ProcessorBase<T>& newElement(const T & t)
{
    v.push_back(t);
    return *this;
}   
virtual T process()=0;  
friend ostream& operator<< <>(ostream & output, const ProcessorBase<T> & o);
};

template<class T>
ostream& operator<<(ostream & output, const ProcessorBase<T> & o)
{
for (std::vector<T>::iterator it = o.v.end() ; it != o.v.begin() && it >10+o.v.begin(); --it)
output<<*it<<endl;
return output;
}

template<class T>
class ProcessorSummer: public ProcessorBase<T>
{
public:
T process()
{
    T sum=0; 
    for (std::vector<T>::iterator it = ProcessorBase<T>::v.begin() ; it != ProcessorBase<T>::v.end(); ++it)
        sum=sum+ *it;
    return sum;
}        
};

template <class T>
void test(T n = 200)
{
ProcessorSummer<T> ps;
for(T k=0;k<n ;++k)
{
    T t= (k / static_cast<T>(2));
    ps.newElement(t);
}
cout<<ps.process()<<endl;
cout<<ps.v<<endl;
}

int main()
{   
    test<int>();
    test<double>();
    test<float>(3);
    system("PAUSE");
    return 0;
}

编译失败：

 error C2248: 'ProcessorBase<T>::v' : cannot access protected member declared in class 'ProcessorBase<T>'

 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::vector<_Ty>' (or there is no acceptable conversion)

你能帮我查一下确切的问题吗？

Answer 1

arr包含指针，因此您无法使用.，需要->。

使用虚方法的模板类

1 个答案: