Qt c++ aggregate 'std::stringstream ss' has incomplete type and cannot be defined

I have this function in my program that converts integers to strings:

    QString Stats_Manager::convertInt(int num)
    {
        stringstream ss;
        ss << num;
        return ss.str();
    }

But when ever i run this i get the error:

aggregate 'std::stringstream ss' has incomplete type and cannot be defined

Im not really sure what that means. But if you know how to fix it or need any more code please just comment. Thanks.

You probably have a forward declaration of the class, but haven't included the header:

#include <sstream>

//...
QString Stats_Manager::convertInt(int num)
{
    std::stringstream ss;   // <-- also note namespace qualification
    ss << num;
    return ss.str();
}

Like it's written up there, you forget to type #include <sstream>

#include <sstream>
using namespace std;

QString Stats_Manager::convertInt(int num)
{
   stringstream ss;
   ss << num;
   return ss.str();
}

You can also use some other ways to convert int to string, like

char numstr[21]; // enough to hold all numbers up to 64-bits
sprintf(numstr, "%d", age);
result = name + numstr;

check this!