[SOLVED] Container Classes - QVector problem

maximus

I have been pulling my hair on this one

I have a QVector<UserStudio>, UserStudio being a custom object

I am following this doc so that my Object can be copied in a Container
but when I copy my QVector, I loose some attribute on my custom Object (attributes that are not primitive type). I have created a copy constructor, but no success. Anyone got this problem before? Thanks

class Employee
{
public:
	Employee() {}
	Employee(const Employee &other);

	Employee &operator=(const Employee &other);

private:
	QString myName;
	QDate myDateOfBirth;
            PowerCurve powerCurve;  //Custom object that get lost during copy!
};

Here is my real class

Chris Kawa

Do you actually copy that member in the copy constructor of your class (you only attached a header so I can't say)?

Does PowerCurve have a proper copy constructor? If not and it's not a POD then the compiler generated copy constructor of it will not do the right thing.

I loose some attribute on my custom QObject

What QObject? I don't see any in your code. In any case QObjects are not copyable.

maximus

I think you found the problem.
The class "PowerCurve" is also a custom Object (not QObject, sorry)

I have defined theses 2 constructors in Power Curve:

PowerCurve();
PowerCurve( const PowerCurve& other );

For some reason, it uses the empty constructor and reset my PowerCurve object attribute when I copy the QVector<UserStudio>. Trying to find a good way to fix this because I need the empty constructor also for default values.

Here are the full cpp
UserStudio.cpp
PowerCurve.cpp

PowerCurve reset in action:
Before (PowerCurve is set):

for (int i=0; i<vecUserStudio.size(); i++) {
    UserStudio userStudio = vecUserStudio.at(i);
    qDebug() << "User Studio power Curve is_Main:" << userStudio.getPowerCurve().getFullName() << userStudio.getPowerCurve().getId() << "test att:" << userStudio.getDisplayName();
}

After Copying QVector (PowerCurve back to default..)

for (int i=0; i<vecUserStudio.size(); i++) {
    UserStudio userStudio = vecUserStudio.at(i);
    qDebug() << "User Studio power Curve is_AfterCopy:" << userStudio.getPowerCurve().getFullName() << userStudio.getPowerCurve().getId() << "test att:" << userStudio.getDisplayName();
}

Log:
User Studio power Curve is_Main: " Kinetic - Road Machine" 59 test att: "Max"
User Studio power Curve is_AfterCopy: "- - TrainerNotSet" 0 test att: "Max"

Here is how I update the PowerCurve in the QVector :

UserStudio myUserStudio = vecUserStudio.at(riderID-1);

myUserStudio.setUsingPowerCurve(true);
myUserStudio.setCompanyID(company_id);
myUserStudio.setBrandID(trainer_id);

PowerCurve myCurve;
myCurve.setId(trainer_id);
myCurve.setName(companyName, trainerName);
myCurve.setCoefs(coef0, coef1, coef2, coef3);
myCurve.setFormulaInCode(formulaInCode);

myUserStudio.setPowerCurve(myCurve);
vecUserStudio.replace(riderID-1, myUserStudio);

Chris Kawa

You've got this in your copy constructor:

this->powerCurve = other.powerCurve;

but that is not calling a copy constructor PowerCurve::PowerCurve( const PowerCurve&). powerCurve is first default constructed and then you call an assignment operator (which you haven't specified so a compiler generates a bad one for you).

If you want to use a copy constructor here then you need to use the initialization list like this:

UserStudio::UserStudio( const UserStudio& other )
   : powerCurve(other.powerCurve), /* other fields ... */
{}

but I suggest you implement PowerCurve& PowerCurve::operator=(const PowerCurve&) anyway.

There's a rule of thumb in C++ called rule of three : destructor, copy constructor, copy assignment operator - if you implement any of these you should probably implement all of them or bugs will follow.

maximus

Thanks for the help Chris,

Finally the problem was just another function overwriting the PowerCurve, so not related with Copy Constructor, etc. I left the default copy constructor that are generated to save coding time, the Objects are just POD so the default is good for me.