How to get all data from QStandardItem ?

Dariusz

Hey
How can I get all roles/data for given item in QStandardItem ? I want to serialize it all.

Regards
Dariusz

Fixed, example code >

i = QStandardItem("hello")
i.setData("dasdas", 15241)
i.setData(5325, 15242)
i.setData(["vdsvds"], 15243)
i.setData(["vdsvds"], 15245)

ar = QByteArray()
s = QDataStream(ar, QIODevice.WriteOnly)
i.write(s)
r = QDataStream(ar, QIODevice.ReadOnly)
val = 0
v = r.readUInt32()
for a in range(v):
    role = r.readInt32()
    var = r.readQVariant()
    print(role, var)

JonB

@Dariusz
It is hidden from you in private code. A vector of <role-number, value> is how it is stored and serialized. The only way you can inspect this --- and thereby get the role names used for each item --- is by doing the serialization to QDataStream per my above and then using your own structures/code to read it back, so that you can access the elements and get the roles. See Qt source for this, e.g. https://codebrowser.dev/qt5/qtbase/src/gui/itemmodels/qstandarditemmodel_p.h.html#_ZlsR11QDataStreamRK17QStandardItemData

JonB

@Dariusz
void QStandardItem::write(QDataStream &out) const

Writes the item to stream out. Only the data and flags of the item are written, not the child items.

Dariusz

Mmm I was hoping to save it to json or something, there is no way to get list of roles to loop over manually?

Christian Ehrlicher

@Dariusz said in How to get all data from QStandardItem ?:

there is no way to get list of roles to loop over manually?

You know which roles you're setting so you can also iterate over them.

Dariusz

@Christian-Ehrlicher Well, partially. User might set custom roles which I wont be able to track. So I'd like to query roles from item...

Christian Ehrlicher

@Dariusz said in How to get all data from QStandardItem ?:

User might set custom roles

I thought you're doing the programming, not the user...

Anyway - derive from QStandardItemModel and remember the roles which are getting set.

Dariusz

@Christian-Ehrlicher Ok to summarize, there is no "getRoles" way of getting roles from QStandardItem and I have to implement it :- )

Will work on that, thanks!

JonB

@Dariusz
It is hidden from you in private code. A vector of <role-number, value> is how it is stored and serialized. The only way you can inspect this --- and thereby get the role names used for each item --- is by doing the serialization to QDataStream per my above and then using your own structures/code to read it back, so that you can access the elements and get the roles. See Qt source for this, e.g. https://codebrowser.dev/qt5/qtbase/src/gui/itemmodels/qstandarditemmodel_p.h.html#_ZlsR11QDataStreamRK17QStandardItemData

Dariusz

Hey @JonB

Mmm tried, I don't think its working in pyside2

i = QStandardItem("hello")
i.setData("dasdas", 15241)
i.setData(5325, 15242)
i.setData(["vdsvds"], 15243)

ar = QByteArray()
s = QDataStream(ar)
i.write(s)
print(ar)

Got an empty buffer.
Regards
Dariusz

JonB

@Dariusz
I don't know, but I would flush & close the data stream before I relied on whatever might be in the array.

I also don't know for sure how this works when you have no model.

Dariusz

Hey @JonB yep I messed up, forgot to specify stream mode

i = QStandardItem("hello")
i.setData("dasdas", 15241)
i.setData(5325, 15242)
i.setData(["vdsvds"], 15243)
i.setData(["vdsvds"], 15245)

ar = QByteArray()
s = QDataStream(ar, QIODevice.ReadWrite)
i.write(s)
r = QDataStream(ar, QIODevice.ReadOnly)
val = 0
v = r.readInt32()
for a in range(v):
    print(r.readInt32())
print(v)

I've digged in to the streaming. Looks to be a bit more of a pain to de-stream it tbh. Tricky.
Its not a list of roles
its role, data, role, data, role, data etc etc

JonB

@Dariusz
But I said earlier

A vector of <role-number, value> is how it is stored and serialized.

Is it not exactly that? And you can deserialize into a QVector.

Dariusz

@JonB I'm in python, I cant just do stream >> QVector<QStandardItemData> I'm afraid :/
I'd have to deserialize each data object by hand to find correct offset byte to next role in vector I think

Update!
Welp turns out there is readQVariant!

i = QStandardItem("hello")
i.setData("dasdas", 15241)
i.setData(5325, 15242)
i.setData(["vdsvds"], 15243)
i.setData(["vdsvds"], 15245)

ar = QByteArray()
s = QDataStream(ar, QIODevice.ReadWrite)
i.write(s)
r = QDataStream(ar, QIODevice.ReadOnly)
val = 0
v = r.readUInt32()
for a in range(v):
    role = r.readInt32()
    var = r.readQVariant()
    print(role, var)
print(v)

This works, wop wop!