#include<iostream>
#include<cstdlib>
using namespace std;
template<class T>
class data1
{
private:
T* date;
int size;
public:
data1(int n=0);
~data1();
data1(const data1<T>& cp);
data1<T>& operator=(const data1<T>& cp);
T get(int _size);
friend istream& operator>>(istream& in, data1<T>& cp);
friend ostream& operator<<(ostream& out, data1<T>& cp);
};
template<class T>
data1<T>::data1(int n):size(n)
{
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = rand() % 100;
}
}
template<class T>
data1<T>::~data1()
{
if (date != 0)
delete[]date;
}
template<class T>
data1<T>::data1(const data1<T>& cp)
{
size = cp.size;
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = cp.date[i];
}
}
template<class T>
data1<T>& data1<T>::operator=(const data1<T>& cp)
{
if (date != 0)
delete[]date;
size = cp.size;
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = cp.date[i];
}
}
template<class T>
T data1<T>::get(int _size)
{
return date[_size];
}
template<class T>
istream& operator>>(istream& in, const data1<T>& cp)
{
in >> cp.size;
for (int i = 0; i <cp.size; i++)
{
in >> cp.date[i];
}
return in;
}
template<class T>
ostream& operator<<(ostream& out,const data1<T>& cp)
{
out << "输出元素个数为：" << cp.size << endl;
for (int i = 0; i < cp.size; i++)
{
out >> cp.date[i]<<" ";
}
return out;
}
int main()
{
data1<int> bu9(5);
cin >> bu9//调用重载输入模板，出现无法解析外部符号，这是为什么呢？
cout << bu9;
return 0;
}
将友元函数在模板类内部实现就好了，再Effective C++条款45中，有详细解释
FYI: https://stackoverflow.com/questions/10787655/c-friend-declaration-declares-a-non-template-function
#include<iostream>
#include<cstdlib>
using namespace std;
template<class T>
class data1
{
private:
T* date;
int size;
public:
data1(int n=0);
~data1();
data1(const data1<T>& cp);
data1<T>& operator=(const data1<T>& cp);
T get(int _size);
friend istream& operator>>(istream& in, data1& cp)
{
in >> cp.size;
for (int i = 0; i <cp.size; i++)
{
in >> cp.date[i];
}
return in;
}
friend ostream& operator<<(ostream& out, data1 const& cp)
{
out << "输出元素个数为：" << cp.size << endl;
for (int i = 0; i < cp.size; i++)
{
out << cp.date[i] <<" ";
}
return out;
}
};
template<class T>
data1<T>::data1(int n):size(n)
{
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = rand() % 100;
}
}
template<class T>
data1<T>::~data1()
{
if (date != 0)
delete[]date;
}
template<class T>
data1<T>::data1(const data1<T>& cp)
{
size = cp.size;
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = cp.date[i];
}
}
template<class T>
data1<T>& data1<T>::operator=(const data1<T>& cp)
{
if (date != 0)
delete[]date;
size = cp.size;
date = new T[size];
for (int i = 0; i < size; i++)
{
date[i] = cp.date[i];
}
}
template<class T>
T data1<T>::get(int _size)
{
return date[_size];
}
/*
template<class T>
istream& operator>>(istream& in, data1<T>& cp)
{
in >> cp.size;
for (int i = 0; i <cp.size; i++)
{
in >> cp.date[i];
}
return in;
}
template<class T>
ostream& operator<<(ostream& out, data1<T> const& cp)
{
out << "输出元素个数为：" << cp.size << endl;
for (int i = 0; i < cp.size; i++)
{
out >> cp.date[i]<<" ";
}
return out;
}
*/
int main()
{
data1<int> bu9(5);
cin >> bu9;//调用重载输入模板，出现无法解析外部符号，这是为什么呢？
cout << bu9;
return 0;
}
// Output
4
101 102 103 104
输出元素个数为：4
101 102 103 104
声明为 友元函数即可，h和cpp写在一起，成为hpp文件会比较好，望采纳，不懂的可以关注私信我。
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