Problem in writing to a file

[darlene]

Hello! i am new to Qt and i have a problem in writing to a file.

when i specify ReadOnly, it seems to be fine. it can open and read the contents of the file. but if i write WriteOnly or ReadWrite, it cannot even open the file. Why is that so?

hope you can help me on this. BTW, i got the code from the Qt documentation.

Thanks.

[Lykurg]

Obviously you don't have the write permission for the file.

[squidge]

Or perhaps even the directory. If you are writing on Windows 7 for example, directories such as Program Files are read only unless you request permission from the user via UAC.

[darlene]

Thanks for your reply.

it is just a text file i added as a resource file. Can we not write on resource files?

my code looks like this

QFile file(":/files/fav.txt");   
    if (!file.open(QIODevice::ReadWrite | QIODevice::Text)){
        qDebug("file not opened");
        qDebug(file.errorString().toStdString().c_str());
        return;
    }

QFile file(":/files/fav.txt");   
    if (!file.open(QIODevice::ReadWrite | QIODevice::Text)){
        qDebug("file not opened");
        qDebug(file.errorString().toStdString().c_str());
        return;
    }

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and the output of the errorString is "Unknown error".

[squidge]

Resources are part of your applications executable. If you were to write to them it would destroy the applications integrity, therefore writing is not allowed.

[darlene]

hello. thank you very much..

if that is the case, how do i save a file (like a .json file) that will be downloaded from the internet to be used by my mobile app?

where are those files saved?

[squidge]

That depends on whether you need to store it after your application has exited or not. Most mobile apps have access to at least some NV storage.

[darlene]

I see.

Yes, the file is going to be used by the app so it needs to be saved. The problem is i have no idea where should it be saved.

i really have no idea on this. Thank you very much for the reply.

[squidge]

You shouldn't need to specify a location as the default is typically your private storage area.

[DanH]

http://doc.qt.nokia.com/4.7/qdir.html#homePath