Question

I’m creating a class in Qt. But everything was working until I built a tablemodel class. I’m now getting the errors "expected ( before * token” and "Creator does not name a type".
What’s the problem? It seems very cryptic.

#ifndef OPENMODEL_H
#define OPENMODEL_H

#include <QAbstractTableModel>
#include <QString>
#include <QObject>

#include "creator.h"

namespace language
{
    class OpenModel : public QAbstractTableModel
    {
        Q_OBJECT

    public:
        explicit OpenModel(Creator* creator, QObject *parent = 0); // Creater* throws a expected ) before * token

        // QAbstractTableModel Model view functions
        int rowCount(const QModelIndex &parent = QModelIndex()) const ;
        int columnCount(const QModelIndex &parent = QModelIndex()) const;
        QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
        QVariant headerData(int section, Qt::Orientation orientation, int role) const;

        // QAbstractTableModel Model edit functions
        bool setData(const QModelIndex & index, const QVariant & value, int role);
        Qt::ItemFlags flags(const QModelIndex &index) const;

        // Functions to manipulate creator
        void add(QString name, QString file);
        void remove(int index);

        // Functions to move files up and down
        void moveup(int index);
        void movedown(int index);

    private:
        Creator* creator; // Creator does not name a type

    };
}

#endif // OPENMODEL_H

this is creator.h

/*
  This is the main file for the language-creator

  It controls the addition, deletion and change of the centances (files)
  It shall be passed by pointer to the models to be proccessed
  */

#ifndef CREATOR_H
#define CREATOR_H

#include <QObject>
#include <QVector>

#include "file.h"
#include "openmodel.h"
#include "setmodel.h"

namespace language
{
    class Creator
    {

    public:
        Creator();

        void addFile(const File& f); // Adds a file to the vector
        bool removeFile(int index); // Remove a file from the vector
        bool replaceFile(int index, const File& f); // Replaces a file at index

        const QVector<File>* getFiles() const; // Returns a list of the files

        OpenModel getOpenModel() const; // Returns a pointer to the open model
        SetModel getSetModel() const; // Returns a pointer to the set model

        void reset(); // This resets the class to an initialized state

    private:
        QVector<File> files; // This holds all the files
    };
}

#endif // CREATOR_H

Answer 1

You have a cyclic reference between these header-files. openmodel.h includes creator.h and the other way around. So, when creator.cpp (I presume there is such a file) gets compiled, it will include openmodel.h before the class Creator is declared (remember that #include means that the contents of the file will be pasted right there), hence you get the error.

To avoid this, you could remove the #include "creator.h" from openmodel.h, and instead add a forward declaration:

class Creator;

Put the declaration right before the class OpenModel. Since you only use pointers to Creator in that class, this will work fine.