How declare an enum that is in another class?

Question

I have an enum in one class :

class SettingManager : public QObject
{
    Q_OBJECT
public:
    enum BookDisplayKinds{
        BookDisplay1=0,
        BookDisplay2=1,
    };
    Q_ENUMS(BookDisplayKinds)
};

I want to declare an property in another class

#include<settingmanager.h>
class BookManager : public NetworkManager
{
  private:    
     SettingManager::BookDisplayKinds m_BookDisplayKind;//Error is here
};

but I got below error:

'SettingManager' does not name a type

I add forward delcalration of SettingManager before BookManager

#include<settingmanager.h>
class SettingManager;
class BookManager : public NetworkManager
{
  private:    
     SettingManager::BookDisplayKinds m_BookDisplayKind;//Error is here
};

But now I have below error

'BookDisplayKinds' in 'class SettingManager' does not name a type

Answer 1

You can switch to strong enum available since C++11. I recommend you to put it out of the class.

// SettingManager.h header
enum class BookDisplayKinds{
        BookDisplay1=0,
        BookDisplay2=1,
};
class SettingManager : public QObject
{
    Q_OBJECT
public:
};

Now it is possible to do a forward declaration like this:

// BookManager.h header
enum class BookDisplayKinds; // forward declaration
class BookManager : public NetworkManager
{
  private:    
     BookDisplayKinds m_BookDisplayKind;/
};