c++ - removeRows() and QPersistentModelIndex -


i have implemented own qabstractlistmodel based on std::vector. want display contents of model in qgraphicsscene. have implemented own qgraphicsitem stores qpersistentmodelindex pointer data.

i have implemented removerows method follows:

bool vectormodel::removerows(int row, int count, const qmodelindex& parent) {     if (row + count < _vector.size()) {         beginremoverows(qmodelindex(), row, row + count);         _vector.erase(_vector.begin() + row, _vector.begin() + row + count);         endremoverows();         return true;     }     return false; }

now since erase elements, index of following elements change. because of qpersistentmodelindex needs adjusted.

i have found changepersistentindex() method in qabstractitemmodel , know can persistent indices persistentindexlist(). don't know how adjust indices accordingly using method. how can done?

will changing these indices enough prevent invalid index errors?

update

i have changed removerows() enhancements of @sebastian lange, still not working expected , receive invalid index errors:

bool labelmodel::removerows(int row, int count, const qmodelindex& parent) {     q_unused(parent)     if (row + count < _vector.size()) {         beginremoverows(qmodelindex(), row, row + count);         _vector.erase(_vector.begin() + row, _vector.begin() + row + count);         endremoverows();          auto pil = persistentindexlist();         for(int = 0; < pil.size(); ++i)         {             if (i >= row + count) {                 changepersistentindex(pil[i], pil[i-count]);             }         }         return true;     }     return false; }

the emitted errors (when removing 7th element):

qabstractitemmodel::endremoverows:  invalid index ( 7 , 1 ) in model qabstractlistmodel(0x101559320) qabstractitemmodel::endremoverows:  invalid index ( 8 , 1 ) in model qabstractlistmodel(0x101559320) qabstractitemmodel::endremoverows:  invalid index ( 9 , 1 ) in model qabstractlistmodel(0x101559320) qabstractitemmodel::endremoverows:  invalid index ( 10 , 1 ) in model qabstractlistmodel(0x101559320) qabstractitemmodel::endremoverows:  invalid index ( 6 , 1 ) in model qabstractlistmodel(0x101559320)

well, not need fiddle changepersistentindex, calling beginremoverows , endremoverows automatically update persistent indexes existing on model. invalid qpersistentmodelindex should have after removing rows index on rows have been deleted


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