When trying to insert items into my QAbstractItemModel:
Qt Code: 
  1. ListModel * model = new ListModel();
  2.     for (int row = 0; row < 4; ++row) {
  3.         for (int column = 0; column < 4; ++column) {
  4.             model->insertRow(1);
  5.             qDebug() << model->setData(model->index(row),QVariant::QVariant("halooo"),Qt::EditRole);
  6.             qDebug() << model->data(model->index(row),Qt::EditRole);
  7.         }
  8.     }
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Outputs:
Qt Code: 
  1. false 
  2. QVariant(Invalid) 
  3. false 
  4. QVariant(Invalid) 
  5. false 
  6. QVariant(Invalid) 
  7. false 
  8. QVariant(Invalid) 
  9. false 
  10. QVariant(Invalid) 
  11. false 
  12. QVariant(Invalid) 
  13. false 
  14. QVariant(Invalid) 
  15. false 
  16. QVariant(Invalid) 
  17. false 
  18. QVariant(Invalid) 
  19. false 
  20. QVariant(Invalid) 
  21. false 
  22. QVariant(Invalid) 
  23. false 
  24. QVariant(Invalid) 
  25. false 
  26. QVariant(Invalid) 
  27. false 
  28. QVariant(Invalid) 
  29. false 
  30. QVariant(Invalid) 
  31. false 
  32. QVariant(Invalid)
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listmodel.h
Qt Code: 
  1. #ifndef LISTMODEL_H
  2. #define LISTMODEL_H
  3.  
  4. #include <QAbstractListModel>
  5. #include <QStringList>
  6.  
  7. class ListModel : public QAbstractListModel
  8. {
  9.     Q_OBJECT
  10. public:
  11.     explicit ListModel(QObject *parent = 0);
  12.     int rowCount( const QModelIndex & parent ) const;
  13.     QVariant data( const QModelIndex & index, int role /* = Qt::DisplayRole*/ ) const;
  14.     Qt::ItemFlags ListModel::flags(const QModelIndex &index) const;
  15.     bool setData(const QModelIndex &index,const QVariant &value, int role);
  16.  
  17. private:
  18.     QStringList stringList;
  19.  
  20. signals:
  21.  
  22. public slots:
  23.  
  24. };
  25.  
  26. #endif // LISTMODEL_H
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listmodel.cpp
Qt Code: 
  1. #include "listmodel.h"
  2. #include <QtDebug>
  3.  
  4. ListModel::ListModel(QObject *parent) :
  6. {
  7. }
  8.  
  9. QVariant ListModel::data( const QModelIndex & index, int role /* = Qt::DisplayRole*/ ) const
  10. {
  11.     // if an invalid row, return empty QVariant
  12.     if (index.row() < 0 || index.row() >= 4)
  13.         return QVariant();
  14.  
  15.     switch( role )
  16.     {
  17.         case Qt::DisplayRole:
  18.         case Qt::EditRole:
  19.         {
  21.             s = QString("row [%1]").arg( index.row() );
  22.             return QVariant(s);
  23.         }
  24.         default:
  25.             return QVariant();
  26.     }
  27. }
  28.  
  29. bool ListModel::setData(const QModelIndex &index,
  30.                               const QVariant &value, int role)
  31. {
  32.     if (index.isValid() && role == Qt::EditRole) {
  33.  
  34.         stringList.replace(index.row(), value.toString());
  35.         emit dataChanged(index, index);
  36.         return true;
  37.     }
  38.     return false;
  39. }
  40.  
  41. Qt::ItemFlags ListModel::flags(const QModelIndex &index) const
  42. {
  43.     if (!index.isValid())
  44.         return Qt::ItemIsEnabled;
  45.  
  46.     return QAbstractItemModel::flags(index)  /*|Qt::ItemIsEditable*/;
  47. }
  48.  
  49. int ListModel::rowCount(const QModelIndex &parent) const
  50. {
  51.     return stringList.count();
  52. }
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It seems like the index passed is never valid, "index.isValid()", so it never sets the data. What's wrong here?