printing the contents of function template taking class pointer - c++

Question

I have difficulty in printing the string value present in a class used inside a function template.
Following is the code
#include <iostream>
#include <string>
#include <vector>
#include <iterator>
using namespace std;
template <typename T>
class Test1{
public:
int val1 = 10;
string val2 = "hello";
};
class Test2{
public:
int val1 = 20;
string val2 = "hai";
};
class Queue{
public:
void append(T & item)
{
{
std::lock_guard<std::mutex> lock(mutex);
cout<<"string to be added "<<item->val2;
mQueue.push_back(item);
}
}
private:
std::vector<T> mQueue;
};
int main(int argc, char** argv) {
Test2 *new_val;
Queue *data;
data->append(new_val);
return 0;
}
Can anyone pl point out the error and what can be done to print the strings of various classes inside the function template.

Answer 1

Attention: when you write
template <typename T>
class Test1{
public:
int val1 = 10;
string val2 = "hello";
};
class Test2{
public:
int val1 = 20;
string val2 = "hai";
};
// ...
you define Test1 as a template class, Test2 and the following classes as ordinary (not template) classes.
So, when you write
class Queue{
public:
void append(T & item)
{
{
std::lock_guard<std::mutex> lock(mutex);
cout<<"string to be added "<<item->val2;
mQueue.push_back(item);
}
}
private:
std::vector<T> mQueue;
};
the compiler doesn't know what is T because T is the template parameter of Test1.
I suppose you want a template Queue
template <typename T>
class Queue{
// ...
};
// ...
Test2 new_val;
Queue<Test2> data;
data.append(new_val);
Observe that I've also trasformed the pointers in object.
Suggestion: avoid pointer until it's clear to you as use they.