Qstring to const char*

QString str(“hello world!”);
Turn into const char *

1. const char * arr = str.toStdString.c_str();
2. const char * arr = str.toLatin1().constData(); //toUtf8()

Turn into char *
3. char * arr = str.toStdString.data();
4. char * arr = str.toLatin1().data(); //toUtf8()

…

Specially ,char * turn QString It's simpler

1. QLatinlString(const char *) -> QString(QLatinlString str)
2. QString(const char *)
3. QString QString::fromStdString(const std::string &str)