qDebug() not showing const std::string&

问题

I am trying to use some vector data's name with struct. I am trying to get see which name in qDebug()

To be more clear:

const std::string& testName = "asdfqwer";
qDebug() << testName;

It gives en error message in build:

Error: no match for 'operator<<' in 'qDebug()() << testName'

I don't have options to change const std::string& type. Could you please help me to solve this issue without changing type?

回答1:

qDebug() does not know anything about std::string but it works with const char*. Appropriate operator you can find here. You can achieve this with data() or with c_str() which is better as Jiří Pospíšil said.

For example:

const std::string& testName = "asdfqwer";
qDebug() << testName.data() << testName.c_str();

Aslo you can convert std::string to QString with QString::fromStdString.

回答2:

If you need writing std::string to qDebug() often in your code, you can implement this function globally (for example in you main.cpp):

#include <QDebug>
#include <string>

QDebug operator<<(QDebug out, const std::string& str)
{
    out << QString::fromStdString(str);
    return out;
}

int main()
{
    std::string jau = "jau";
    qDebug() << jau;
    return 0;
}

来源：https://stackoverflow.com/questions/27358828/qdebug-not-showing-const-stdstring