I created a TableModel which extends QAbstractTableModel and whenever I double click inside a cell to edit it, if it has a current value, that value gets erased, I've tried overwriting the double click signal and resetting the value, but that didn't help.

I've included all the files I'm using.

model.h
http://pastebin.com/V7VJAuCJ

model.cpp
http://pastebin.com/zPjSViFQ

MainWindow.h
http://pastebin.com/kGGp06zH

MainWindow.cpp
http://pastebin.com/wuRaQ3eE


Model.cpp
Qt Code: 
  1. #include <QtGui>
  2.  
  3. #include "model.h"
  4. #include <QDebug>
  5.  
  6. /*!
  7.     Constructs a table model with at least one row and one column.
  8. */
  9.  
  10. TableModel::TableModel(int rows, int columns, QObject *parent)
  12. {
  13.     QStringList newList;
  14.  
  15.     for (int column = 0; column < qMax(1, columns); ++column) {
  16.         newList.append("");
  17.     }
  18.  
  19.     for (int row = 0; row < qMax(1, rows); ++row) {
  20.         rowList.append(newList);
  21.     }
  22. }
  23.  
  24.  
  25. /*!
  26.     Returns the number of items in the row list as the number of rows
  27.     in the model.
  28. */
  29.  
  30. int TableModel::rowCount(const QModelIndex &/*parent*/) const
  31. {
  32.     return rowList.size();
  33. }
  34.  
  35. /*!
  36.     Returns the number of items in the first list item as the number of
  37.     columns in the model. All rows should have the same number of columns.
  38. */
  39.  
  40. int TableModel::columnCount(const QModelIndex &/*parent*/) const
  41. {
  42.     return rowList[0].size();
  43. }
  44.  
  45. /*!
  46.     Returns an appropriate value for the requested data.
  47.     If the view requests an invalid index, an invalid variant is returned.
  48.     Any valid index that corresponds to a string in the list causes that
  49.     string to be returned for the display role; otherwise an invalid variant
  50.     is returned.
  51. */
  52.  
  53. QVariant TableModel::data(const QModelIndex &index, int role) const
  54. {
  55.     if (!index.isValid())
  56.         return QVariant();
  57.  
  58.     if (role == Qt::DisplayRole)
  59.         return rowList[index.row()][index.column()];
  60.     else
  61.         return QVariant();
  62. }
  63.  
  64. /*!
  65.     Returns the appropriate header string depending on the orientation of
  66.     the header and the section. If anything other than the display role is
  67.     requested, we return an invalid variant.
  68. */
  69.  
  70. QVariant TableModel::headerData(int section, Qt::Orientation orientation,
  71.                                 int role) const
  72. {
  73.     if (role != Qt::DisplayRole)
  74.         return QVariant();
  75.  
  76.     if (orientation == Qt::Horizontal)
  77.         return QString("Column %1").arg(section);
  78.     else
  79.         return QString("Row %1").arg(section);
  80. }
  81.  
  82. /*!
  83.     Returns an appropriate value for the item's flags. Valid items are
  84.     enabled, selectable, and editable.
  85. */
  86.  
  87. Qt::ItemFlags TableModel::flags(const QModelIndex &index) const
  88. {
  89.     if (!index.isValid())
  90.         return Qt::ItemIsEnabled;
  91.  
  92.     return Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsEditable;
  93. }
  94.  
  95. /*!
  96.     Changes an item in the model, but only if the following conditions
  97.     are met:
  98.  
  99.     * The index supplied is valid.
  100.     * The role associated with editing text is specified.
  101.  
  102.     The dataChanged() signal is emitted if the item is changed.
  103. */
  104.  
  105. bool TableModel::setData(const QModelIndex &index,
  106.                          const QVariant &value, int role)
  107. {
  108.     if (!index.isValid() || role != Qt::EditRole)
  109.         return false;
  110.  
  111.     qDebug()<< value.toString();
  112.     rowList[index.row()][index.column()] = value.toString();
  113.     emit dataChanged(index, index);
  114.     return true;
  115. }
  116.  
  117. /*!
  118.     Inserts a number of rows into the model at the specified position.
  119. */
  120.  
  121. bool TableModel::insertRows(int position, int rows, const QModelIndex &parent)
  122. {
  123.     int columns = columnCount();
  124.     beginInsertRows(parent, position, position + rows - 1);
  125.  
  126.     for (int row = 0; row < rows; ++row) {
  127.         QStringList items;
  128.         for (int column = 0; column < columns; ++column)
  129.             items.append("");
  130.         rowList.insert(position, items);
  131.     }
  132.  
  133.     endInsertRows();
  134.     return true;
  135. }
  136.  
  137. /*!
  138.     Inserts a number of columns into the model at the specified position.
  139.     Each entry in the list is extended in turn with the required number of
  140.     empty strings.
  141. */
  142.  
  143. bool TableModel::insertColumns(int position, int columns, const QModelIndex &parent)
  144. {
  145.     int rows = rowCount();
  146.     beginInsertColumns(parent, position, position + columns - 1);
  147.  
  148.     for (int row = 0; row < rows; ++row) {
  149.         for (int column = position; column < columns; ++column) {
  150.             rowList[row].insert(position, "");
  151.         }
  152.     }
  153.  
  154.     endInsertColumns();
  155.     return true;
  156. }
  157.  
  158. /*!
  159.     Removes a number of rows from the model at the specified position.
  160. */
  161.  
  162. bool TableModel::removeRows(int position, int rows, const QModelIndex &parent)
  163. {
  164.     beginRemoveRows(parent, position, position + rows - 1);
  165.  
  166.     for (int row = 0; row < rows; ++row) {
  167.         rowList.removeAt(position);
  168.     }
  169.  
  170.     endRemoveRows();
  171.     return true;
  172. }
  173.  
  174. /*!
  175.     Removes a number of columns from the model at the specified position.
  176.     Each row is shortened by the number of columns specified.
  177. */
  178.  
  179. bool TableModel::removeColumns(int position, int columns, const QModelIndex &parent)
  180. {
  181.     int rows = rowCount();
  182.     beginRemoveColumns(parent, position, position + columns - 1);
  183.  
  184.     for (int row = 0; row < rows; ++row) {
  185.         for (int column = 0; column < columns; ++column) {
  186.             rowList[row].removeAt(position);
  187.         }
  188.     }
  189.  
  190.     endRemoveColumns();
  191.     return true;
  192. }
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model.h

Qt Code: 
  1. #ifndef MODEL_H
  2. #define MODEL_H
  3.  
  4. #include <QAbstractTableModel>
  5. #include <QStringList>
  6. #include <QVariant>
  7.  
  8. class TableModel : public QAbstractTableModel
  9. {
  10.     Q_OBJECT
  11.  
  12. public:
  13.     TableModel(int rows = 1, int columns = 1, QObject *parent = 0);
  14.  
  15.     int rowCount(const QModelIndex &parent = QModelIndex()) const;
  16.     int columnCount(const QModelIndex &parent = QModelIndex()) const;
  17.     QVariant data(const QModelIndex &index, int role) const;
  18.     QVariant headerData(int section, Qt::Orientation orientation,
  19.                         int role = Qt::DisplayRole) const;
  20.  
  21.     Qt::ItemFlags flags(const QModelIndex &index) const;
  22.     bool setData(const QModelIndex &index, const QVariant &value,
  23.                  int role = Qt::EditRole);
  24.  
  25.     bool insertRows(int position, int rows, const QModelIndex &parent = QModelIndex());
  26.     bool insertColumns(int position, int columns, const QModelIndex &parent = QModelIndex());
  27.     bool removeRows(int position, int rows, const QModelIndex &parent = QModelIndex());
  28.     bool removeColumns(int position, int columns, const QModelIndex &parent = QModelIndex());
  29.  
  30. private:
  31.     QList<QStringList> rowList;
  32. };
  33.  
  34. #endif
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