QString to QString assignment

Bikash_R_Das

Hi,
I m using Qt 6.5.7 for Embedded application.

I have some query related to QString to QString assignment.

I have a structure containg an enumeration data type and two QString s. Something like this:

typedef struct Student {
    GENDER_TYPE    eGender; // possible values GENDER_TYPE_MALE, GENDER_TYPE_FEMALE and GENDER_TYPE_MAX 
    QString strName;
    QString strGroupName;
    Student()
    {
        eGender = GENDER_TYPE_MAX;
        strName = "";
        strGroupName = "";
    }
} Student;

Now say somewhere I have following code:

Student stu1;
stu1.eGender = GENDER_TYPE_MALE;
stu1.strName = "Amit";
stu1.strGroupName = "DOLPHIN";
.
.
Student stu2;
stu2 = stu1;

Is it safe to do stu2 = stu1? Or do I need to have an assignment operator overloading for the structure?
This doubt is related to QString assignment. As per my understanding, it is safe. But any input on the above will be a great help.

Thanks in advance.

JonB

@Bikash_R_Das
Yes you can just assign one struct from the other. As @Ben-Campbell-Wallis writes, QString does shared usage and only detaches/creates an actual copy if you change one of the QStrings. However that has nothing to do with the safety of the struct copy, and it would still be "safe" even if QString did not have this behaviour. This is down to the implementation of QString &QString::operator=(const QString &other) / QString::QString(const QString &other), and the fact that it is inside a whole struct being assigned is not important.

Ben Campbell-Wallis

@Bikash_R_Das I believe QString deep-copy behaviour is implicit (copy-on-write). There's no need for operator overloading.

If in doubt here is the Qt doc:

https://doc.qt.io/qt-6/qstring.html

JonB

@Bikash_R_Das
Yes you can just assign one struct from the other. As @Ben-Campbell-Wallis writes, QString does shared usage and only detaches/creates an actual copy if you change one of the QStrings. However that has nothing to do with the safety of the struct copy, and it would still be "safe" even if QString did not have this behaviour. This is down to the implementation of QString &QString::operator=(const QString &other) / QString::QString(const QString &other), and the fact that it is inside a whole struct being assigned is not important.

Bikash_R_Das

Thanks @Ben-Campbell-Wallis and @JonB for the reply.