expected class-name before ‘{’ token

碰到过几次这类问题，但是那时也不知道是怎么弄好的，最近在一些帖子，找到了办法，

就是在头文件里，将include "xxx.h"文件注释掉，换成声明，在.cpp文件里使用include "xxx.h"。

具体参考：

http://stackoverflow.com/questions/7199809/expected-class-name-before-token

http://stackoverflow.com/questions/3632818/forward-declaration-vs-include

举例说明：

文件1 cbase.h

#ifndef CBASE_H
#define CBASE_H

#include <QObject>
#include "ctree.h"

class CBase : public QObject
{
    Q_OBJECT
public:
    explicit CBase(QObject *parent = 0);
    CTree *  tree;
signals:

public slots:
};

#endif // CBASE_H

文件2  cmain.h

#ifndef CMAIN_H
#define CMAIN_H

#include <QObject>
#include "cbase.h"
class CMain : public CBase
{
    Q_OBJECT
public:
    explicit CMain(QObject *parent = 0);
signals:

public slots:
};

#endif // CMAIN_H

文件3  ctree.h

#ifndef CTREE_H
#define CTREE_H

#include <QObject>
#include "cbase.h"
#include "cmain.h"

class CTree : public QObject
{
    Q_OBJECT
public:
    explicit CTree(QObject *parent = 0);
    CBase * bs;
    CMain * mnt;
signals:

public slots:
};

#endif // CTREE_H

便以结果：
In file included from ctree.h:6:0,
                 from cbase.h:5,
                 from cbase.cpp:1:
cmain.h:8:1: error: expected class-name before ‘{’ token

多个文件相互嵌套包含时，会提示：expected class-name before ‘{’ token，

有时即使头文件里添加了#ifndef XX #define XX;还是没用，

解决方法：在文件3  ctree.h添加类说明

class CBase;
class CMain;

,注释掉include

#ifndef CTREE_H
#define CTREE_H

#include <QObject>

//#include "cbase.h"
//#include "cmain.h"
class CBase;
class CMain;

class CTree : public QObject
{
    Q_OBJECT
public:
    explicit CTree(QObject *parent = 0);
    CBase * bs;
    CMain * mnt;
signals:

public slots:
};

#endif // CTREE_H