Subclassing an Implementattion of QAbstractItemModel

[ob019]

Hello everybody,
i am a newbie in using the MVC-Classes of QT4. (4.3.4) I have got the following problem:

I provide an implementation of QAbstactItemModel named MyModel. This Model works fine.

class MyModel :  public QAbstractItemModel
{
    Q_OBJECT
 
public:
    MyModel( const QString &filename, QObject* parent = 0 );
    ~MyModel();  
 
    /*
    ** AbstractItemModel(required methods)
    */
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole ) const;
    QModelIndex index(int row, int col, const QModelIndex &parent = QModelIndex() ) const;
    QModelIndex parent(const QModelIndex &index ) const;
    int rowCount(const QModelIndex &parent = QModelIndex() ) const;
    int columnCount(const QModelIndex &parent = QModelIndex() ) const;
    QVariant headerData(int section, Qt::Orientation orientation,
        int role = Qt::DisplayRole) const;
 
    Qt::ItemFlags flags(const QModelIndex &index) const;
    bool setData(const QModelIndex &index, const QVariant &value,
                  int role = Qt::EditRole);
private:
    void setupModel();
    .
    .
    .
};

class MyModel :  public QAbstractItemModel
{
    Q_OBJECT

public:
    MyModel( const QString &filename, QObject* parent = 0 );
    ~MyModel();  

    /*
    ** AbstractItemModel(required methods)
    */
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole ) const;
    QModelIndex index(int row, int col, const QModelIndex &parent = QModelIndex() ) const;
    QModelIndex parent(const QModelIndex &index ) const;
    int rowCount(const QModelIndex &parent = QModelIndex() ) const;
    int columnCount(const QModelIndex &parent = QModelIndex() ) const;
    QVariant headerData(int section, Qt::Orientation orientation,
        int role = Qt::DisplayRole) const;

    Qt::ItemFlags flags(const QModelIndex &index) const;
    bool setData(const QModelIndex &index, const QVariant &value,
                  int role = Qt::EditRole);
private:
    void setupModel();
    .
    .
    .
};

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Now I want to subclass from this bassclass to create a new model called MyTXTModel.

class MyTXTModel : MyModel
{
    Q_OBJECT
 
public:
    MyTXTModel(const QString& filename, QObject *parent = 0);
    ~MyTXTModel();
 
private:
    .
    .
    .    
};

class MyTXTModel : MyModel
{
    Q_OBJECT

public:
    MyTXTModel(const QString& filename, QObject *parent = 0);
    ~MyTXTModel();

private:
    .
    .
    .    
};

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But this model doesn't work. I get several errors from the linker:

MyTXTModel.obj : error LNK2019: link to unresolved external symbol ""public: __thiscall MyModel::MyModel(class QString const &,class QObject *)" (??0MyModel@@QAE@ABVQString@@PAVQObject@@@Z)" in function ""public: __thiscall MyTXTModel::MyTXTModel(class QString const &,class QObject *)" (??0MyTXTModel@@QAE@ABVQString@@PAVQObject@@@Z)".
MyTXTModel.obj : error LNK2001: unresolved external symbol ""public: virtual class QModelIndex __thiscall MyModel::index(int,int,class QModelIndex const &)const " (?index@MyModel@@UBE?AVQModelIndex@@HHABV2@@Z)".
.
.
.

MyTXTModel.obj : error LNK2019: link to unresolved external symbol ""public: __thiscall MyModel::MyModel(class QString const &,class QObject *)" (??0MyModel@@QAE@ABVQString@@PAVQObject@@@Z)" in function ""public: __thiscall MyTXTModel::MyTXTModel(class QString const &,class QObject *)" (??0MyTXTModel@@QAE@ABVQString@@PAVQObject@@@Z)".
MyTXTModel.obj : error LNK2001: unresolved external symbol ""public: virtual class QModelIndex __thiscall MyModel::index(int,int,class QModelIndex const &)const " (?index@MyModel@@UBE?AVQModelIndex@@HHABV2@@Z)".
.
.
.

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Does anybody have a solution for this problem???

Kind regards

[wysota]

My guess is you didn't run qmake after adding the Q_OBJECT macro to the class declaration.

[ob019]

Hmmm that can't be the problem. I successfully ran qmake and moc_MyTXTModel.cpp is generated.

[stevey]

Have you provided a body for the constructor in a .cpp file?

[ob019]

Ahhh I found my fault!!!
I tried to use Qt's plugin-capabilities for extending my base-model.
So the base-class is in the core-application and the derived class is integrated by using a plugin. I forgot including the base-class to the plugin-project. Stupid error!

But thanks anyway for your ideas guys!!!