Error: iso c ++ forbids declaration of 'xxxx' with no type

This error occurs because two CPP files contain the header file of the other object. For example:

 

When mainwindow. cpp and configdialog. cpp files respectively contain the header files of the other party and declare the objects in their own classes, namely:

 

Mainwindow. cpp

# Include "configdialog. H"

Class mainwindow {

Configdialog * configdialog;

};

 

Configdialog. cpp

# Include "mainwindow. H"

Class configdialog {

Mainwindow * mainwindow;

};

 

The solution is to append the keyword "class" before declaring the Class Name of the object, which is modified as follows:

 

 

Mainwindow. cpp

# Include "configdialog. H"

Class mainwindow {

ClassConfigdialog * configdialog;

};

 

Configdialog. cpp

# Include "mainwindow. H"

Class configdialog {

ClassMainwindow * mainwindow;

};