<![CDATA[Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost?]]>ok. let's find out how well do you know C++.
ok we have

struct StructOfQByteArray1AndQbyteArray2 {
    QByteArray array1;
    QByteArray array2;
}

Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost?

where I want to use this?
when working with QAbstractItemModel I implement method QHash<int, QByteArray> QAbstractItemModel::roleNames() const but in app I have more complex QHash<int, StructOfQByteArray1AndQbyteArray2> with some extra data.

]]>https://forum.qt.io/topic/70207/hot-to-convert-cast-qhash-int-structofqbytearray1andqbytearray2-to-qhash-int-qbytearray1-with-minimum-resource-costRSS for NodeSat, 11 Apr 2026 09:42:27 GMTSat, 13 Aug 2016 12:49:59 GMT60<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Thu, 18 Aug 2016 20:09:36 GMT]]>Ok but these roles are already known, no ?

]]>https://forum.qt.io/post/343066https://forum.qt.io/post/343066Thu, 18 Aug 2016 20:09:36 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Thu, 18 Aug 2016 18:55:47 GMT]]>@SGaist yes, I will have custom roles for some delegates.

]]>https://forum.qt.io/post/343054https://forum.qt.io/post/343054Thu, 18 Aug 2016 18:55:47 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sun, 14 Aug 2016 19:02:47 GMT]]>I'm just saying that you can't cast (as in static_cast, dynamic_cast etc.) such a hash of int and struct to a hash of int and QByteArray.

Are your role names going to be dynamically created ? Changed ?

]]>https://forum.qt.io/post/342267https://forum.qt.io/post/342267Sun, 14 Aug 2016 19:02:47 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sun, 14 Aug 2016 08:15:01 GMT]]>@SGaist Speed. So you want to say that it is ok to manually fill in QHash<int, QByteArray> before returning and just allow data to be copied as rvalue?

]]>https://forum.qt.io/post/342222https://forum.qt.io/post/342222Sun, 14 Aug 2016 08:15:01 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sat, 13 Aug 2016 18:30:17 GMT]]>Hi,

From a C++ POV: you can't do such a cast.

What resources do you want to optimize ? Speed ? Memory use ?

]]>https://forum.qt.io/post/342204https://forum.qt.io/post/342204Sat, 13 Aug 2016 18:30:17 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sat, 13 Aug 2016 13:36:24 GMT]]>@Kofr said:

ahh its something you must return.

Well i think u need copy then since i doubt there is way to cast the original
StructOfQByteArray1AndQbyteArray2

]]>https://forum.qt.io/post/342166https://forum.qt.io/post/342166Sat, 13 Aug 2016 13:36:24 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sat, 13 Aug 2016 13:27:15 GMT]]>@mrjj but I have to return exactly data, not pointer QHash<int, QByteArray> QAbstractItemModel::roleNames() const

]]>https://forum.qt.io/post/342164https://forum.qt.io/post/342164Sat, 13 Aug 2016 13:27:15 GMT<![CDATA[Reply to Hot to convert (cast) QHash<int, StructOfQByteArray1AndQbyteArray2> to QHash<int, QByteArray1> with minimum resource cost? on Sat, 13 Aug 2016 12:54:52 GMT]]>well if u want to avoid copy bytearray
maybe use something like
QHash<int, QByteArray1 *>
and set to point to the real QByteArray1; ?

]]>https://forum.qt.io/post/342161https://forum.qt.io/post/342161Sat, 13 Aug 2016 12:54:52 GMT