Friend class not working

问题:

I am getting the typical '... is private within this context' error. Can you tell me what I am doing wrong? Code is shortened for readability.

in class SceneEditorWidgetController: (settingsdialog and the variable used here is defined in the header)

SceneEditorPluginWidgetController::SceneEditorPluginWidgetController() { } void SceneEditorPluginWidgetController::configured() {     priorKnowledge_setting = settingsDialog->priorKnowledgeProxyFinder->getSelectedProxyName().toStdString(); //This is the context } 

My class SettingsController.h

namespace Ui {     class SettingsController; } namespace GuiController {     class SettingsController : public QDialog     {         Q_OBJECT         friend class SceneEditorPluginWidgetController;     public:         explicit SettingsController(QWidget *parent = 0);         ~SettingsController();      private: //it is private here         Ui::SettingsController* ui;         IceProxyFinderBase* priorKnowledgeProxyFinder;     }; } 

I cannot modify the IceProxyFinderBase class, but it was used exactly (I'm probably blind?) like this before.

Could somebody please explain what I am doing wrong?

回答1:

With an unqualified class name, the friend declaration declares that a class of that name, in the surrounding namespace, is a friend, if such a class exists. So this is equivalent to

friend class GuiController::SceneEditorPluginWidgetController; 

However, your comments say that the class is actually in the global namespace, not GuiController, so this doesn't make it a friend. You'll need to qualify it correctly:

friend class ::SceneEditorPluginWidgetController; 

文章来源: Friend class not working