Hi, I'm learning to develop Akonadi resources.
Everything is going well until I set a custom attribute in collection and I
try to read this attribute in retrieveItem() getting a segmentation
violation for trying to access a null pointer.
This is how I did it:
I extend Akonadi::Attribute class to implement my custom property.
Then, I register my custom attribute in resource constructor:
testResource::testResource( const QString &id )
: ResourceBase( id )
{
// ...
AttributeFactory::registerAttribute<TestAttribute>();
}
When retrieving collections, I set this attribute to collection:
void testResource::retrieveCollections()
{
Collection c;
// ...
TestAttribute *attr = new TestAttribute("value1");
c.addAttribute(attr);
}
I've checked that I can successfully read this value from retrieveItems:
void testResource::retrieveItems( const Akonadi::Collection &collection )
{
TestAttribute *attr = collection.attribute<TestAttribute>();
QByteArray attr_value = attr->serialized();
qDebug("retrieveItems value: %s", attr_value.constData());
// ...
}
But when trying to get attribute from retrieveItem, it gives a null
pointer. So trying to read any class attribute will give a SEGV:
bool testResource::retrieveItem( const Akonadi::Item &item, const
QSet<QByteArray> &parts )
{
TestAttribute *attr = item.parentCollection().attribute<TestAttribute>();
// NULL pointer
QByteArray attr_value = attr->serialized(); // SEGV
qDebug("retrieveItem value: %s", attr_value.constData());
}
I've also tried copying attribute from collection to item in retrieveItems
and then read item attribute in retrieveItem with same result:
void testResource::retrieveItems( const Akonadi::Collection &collection )
{
TestAttribute *attr = collection.attribute<TestAttribute>();
// ...
foreach (Akonadi::Item item, itemList)
item.addAttribute(attr);
// ...
}
bool testResource::retrieveItem( const Akonadi::Item &item, const
QSet<QByteArray> &parts )
{
TestAttribute *attr = item.attribute<TestAttribute>(); // NULL pointer
QByteArray attr_value = attr->serialized(); // SEGV
qDebug("retrieveItem value: %s", attr_value.constData());
}
In both cases, I've checked with akonadiconsole that attribute is
successfully set, so the problem seems to be accessing to it from
retrieveItem.
I've made a full test project by taking sample agent available at
http://techbase.kde.org/Development/Tutorials/Akonadi/Resources and adding
custom attribute:
http://anongit.chuso.net/testresource/tree/testresource.cpp#n48
Also, the second case adding attribute to item:
http://anongit.chuso.net/testresource/tree/testresource.cpp?h=attribute-on-items#n48
What am I doing wrong? Am I trying to do something that is not possible to
do?
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