QFile - Problem with generated setter

buzz_lightzyear

Hello!

I have a problem with with a member in my program. I have created a lot of members, like QString, QDate, QImage and QFile. Then I have choosen "Create Getter and Setter Member Functions" and the Qt Creator implemented all the getters and setters for me - everything without problems except the QFile-setter. Qt creator shows me an error:

Overload resolution selected deleted operator '='

Here explicit error message:

program.cpp:108:13: Overload resolution selected deleted operator '='
:325:5: note: candidate function has been explicitly deleted

Can someone tell me where the problem is? I have no idea^^^

Thx & Goodbye!

Christian Ehrlicher

Please show the code you're using.

buzz_lightzyear

Here the content of the header:

//program.h
private:
QFile gpxFile;

public:
QFile &getGpxFile() const;
setGpxFile(const QFile &newGpxFile);

...and here the content of the .cpp

const QFile &BikeTour::getGpxFile() const
{
    return gpxFile;
}

void BikeTour::setGpxFile(const QFile &newGpxFile)
{
    gpxFile = newGpxFile;  //Here is the problem. The IDE says: Overload resolution selected deleted operator '='
}

Thank you for your help!

Christian Ehrlicher

@buzz_lightzyear said in QFile - Problem with generated setter:

QFile &getGpxFile() const;

const QFile &BikeTour::getGpxFile() const

These are two different functions.

buzz_lightzyear

ok... can you please tell me exactly where the problem is? I don't see it... otherwise I wouldn't ask here. :-)

Christian Ehrlicher

@buzz_lightzyear said in QFile - Problem with generated setter:

can you please tell me exactly where the problem is?

Simply compare the return values

QFile &

reference

const QFile &

const reference

ChrisW67

Unless I missed something, this code assumes you can copy a QFile object.
In QObject the copy constructor and assignment operator are deliberately disabled (i.e. deleted). QFile is ultimately a QObject.

buzz_lightzyear

Thank you! :-)

buzz_lightzyear

Ok... that was too early. I don't even know why the setter is not working. Can you please give me an example of a working setter for my example? I have checked the return values but I don't come to a resolution. It is not working :-(

Thx in advance!
buzzzzz

JonB

@buzz_lightzyear
QString, QDate and QImage are not QObjects and so can be copied and a setter can be written. QFile however inherits QObject. That means it cannot be copied. You won't be able to do a gpxFile = newGpxFile like for the others. Even though the IDE may let you try to write a setter for it you won't get it to work.

You might perhaps have a pointer to a QObject-derived class (e.g. QFile *) as a member variable with a setter, but that's another matter.

Even if it worked, what would you want to set/copy a QFile for?

buzz_lightzyear

Ok thanks for your answer. The idea behind that is a simple bike-tour logger with a sqlite database in background. After a tour I want to enter the tourdata (eg. odometer...) to get a statistic over my tours over the year. And therefore I want also to upload the GPS generated tour as blob into the database. For that reason I thought a QFile is the best class for that because I don't want to edit the gpx file. But it seems to be hard. Do you have an example for another class?

Thx and goobye,
buzzzzz

mpergand

@buzz_lightzyear
Since you're talking about sqlite, the only information you need is the filepath of the database.
And then, just open and update that database when you needed to.

buzz_lightzyear

@mpergand said in QFile - Problem with generated setter:

@buzz_lightzyear
Since you're talking about sqlite, the only information you need is the filepath of the database.
And then, just open and update that database when you needed to.

thx but I think this is not this what I need now. The database connection is already established.

Christian Ehrlicher

@buzz_lightzyear said in QFile - Problem with generated setter:

The database connection is already established.

So why do you need a QFile object for it then? If you open a sqlite database with Qt you don't need a QFile object at all.

JonB

@buzz_lightzyear said in QFile - Problem with generated setter:

I want also to upload the GPS generated tour as blob into the database. For that reason I thought a QFile is the best class for that

You can use a QFile for this if you wish, you just can't copy/assign via the setter you were trying. As I said earlier, a QFile * could be used in the pattern you are choosing.
Or you could pass e.g. the file path around and use QFile when you need to read in the contents to send as a blob to the database.

buzz_lightzyear

So why do you need a QFile object for it then? If you open a sqlite database with Qt you don't need a QFile object at all.

I need the QFile object for the gpx-file, not for the SQlite database. For that I have the QSqlDatabase class.

buzz_lightzyear

@JonB said in QFile - Problem with generated setter:

@buzz_lightzyear said in QFile - Problem with generated setter:

I want also to upload the GPS generated tour as blob into the database. For that reason I thought a QFile is the best class for that

You can use a QFile for this if you wish, you just can't copy/assign via the setter you were trying. As I said earlier, a QFile * could be used in the pattern you are choosing.

Or you could pass e.g. the file path around and use QFile when you need to read in the contents to send as a blob to the database.

ok thanks... then I will try it this way.

Christian Ehrlicher

@buzz_lightzyear said in QFile - Problem with generated setter:

I need the QFile object for the gpx-file

No you don't as @JonB already told you (several times iirc)