[SOLVED] Saving and reading QMap from QSettings

Zerby

Hello,

I'm trying to store a QMap<QString, QString> to QSettings as bytearray, and then read it back as a QMap object. Here's what I got so far:

QMap<QString,QString> is typedefd as QStringMap

Saving, works:
@
...
QStringMap testmap;
testmap.insert("M1", "Value 1");
testmap.insert("M2", "Value 2");

QByteArray data;
QDataStream *stream = new QDataStream(&data, QIODevice::WriteOnly);

*stream << testmap;
delete stream;

program_settings.setValue("savedMap", data);

...
@

So, this saves the QByteArray to QSettings object with key savedMap. My question is, how do I read construct a QMap from the bytearray stored in the QSettings? I presume I need to use the Related Non-Members:

@QDataStream & operator<<(QDataStream & out, const QMap<Key, T> & map)
QDataStream & operator>>(QDataStream & in, QMap<Key, T> & map)@

found in the QMap documentation, but to be honest I don't know how! Anyone?

andreyc

I think you need to read setting to QByteArray, create QDataStream from QByteArray and read QMap from QDataStream.
Not tested example
@
QByteArray data = program_settings.value("savedMap").toByteArray();
QDataStream *stream = new QDataStream(&data, ReadOnly);
QStringMap testmap;
stream >> testmap;
@

Zerby

[quote author="andreyc" date="1409247208"]I think you need to read setting to QByteArray, create QDataStream from QByteArray and read QMap from QDataStream.
Not tested example
@
QByteArray data = program_settings.value("savedMap").toByteArray();
QDataStream *stream = new QDataStream(&data, ReadOnly);
QStringMap testmap;
stream >> testmap;
@
[/quote]

Thank you! I actually got as far as the last line, somehow just couldn't figure out to use the >> operator (which is ironic, as it's very logical >.< Haven't used streams too much yet..)

So, tested sample snippets:

Writing:
@
QStringMap testmap;
testmap.insert("M1", "Value 1");
testmap.insert("M2", "Value 2");
QByteArray data;
QDataStream stream(&data, QIODevice::WriteOnly);
stream << testmap;
program_settings.setValue("savedMap", data);
@

Reading:
@
QStringMap readMap;
QByteArray readData = program_settings.value("savedMap").toByteArray();
QDataStream readStream(&readData, QIODevice::ReadOnly);
readStream >> readMap;
@

I only used new operator when creating the QDataStream, because an found an example for the writing which said it was needed. But as I tested, it worked just fine like the examples above.

Thank you very much!