Question

在我尝试通过引用将此类传递到另一个类之前编译的代码。你可以忽略我使用QT的事实。

为了完整性，我添加了所有受影响的文件。

所以我以为我已经掌握了前瞻声明。这是我得到的错误，表明编译器对前向声明不满意：

error: field m_systemController has incomplete type
           SystemController m_systemController;

你可以在底部.cpp看到它变形的变量：

这是startup.h：

#pragma once
#include <QObject>

namespace GUI{
    class SetupTab; //Should have my forward declarations in order
    class CbcRegistersTab;
    class DataTestTab;

    class MainView;

    class Settings;

    class SystemController;

    class DataTest;
    class SetupTabViewManager;


    class Startup : public QObject
    {
        Q_OBJECT
    public:
        explicit Startup();
        void show() const ;

        ~Startup();
    private:
        SetupTab& m_setupTab;
        CbcRegistersTab& m_regTab;
        DataTestTab& m_dataTab;

        MainView& m_mainView;
        Settings* m_settings;

        SystemController& m_systemController;

        DataTest& m_dataTest; 

        SetupTabViewManager* m_setupTabVm;

        explicit Startup(const Startup& rhs) = delete;
        Startup& operator= (const Startup& rhs) = delete;
    };
}

这是startup.cpp的开始：

#include "startup.h"
#include "View/setuptab.h"
#include "View/cbcregisterstab.h"
#include "View/datatesttab.h"
#include "View/mainview.h"
#include "Model/settings.h"
#include "Model/systemcontroller.h"
#include "Model/datatest.h"
#include "ViewMgr/setuptabviewmanager.h"
#include "provider.h" 

namespace GUI
{
    Startup::Startup() :
        QObject(nullptr),
        m_setupTab(*new SetupTab(nullptr)),
        m_regTab(*new CbcRegistersTab(nullptr)),
        m_dataTab(*new DataTestTab(nullptr)),

        m_mainView(*new MainView(nullptr,
                                 m_setupTab,
                                 m_regTab,
                                 m_dataTab)),

        m_systemController(*new SystemController(nullptr,
                                                 Provider::getSettingsAsSingleton())),

        m_dataTest(*new DataTest(nullptr,
                                m_systemController)), //so it's this part I'm having trouble with

        m_setupTabVm(new SetupTabViewManager(this,
                                             m_setupTab,
                                             m_systemController,
                                             Provider::getSettingsAsSingleton() ))

然后我很简单地将这个值传递给我的datatest.h并通过引用将它绑定到一个变量：

#pragma once
#include <QObject>

namespace GUI{

    class SystemController;

    class DataTest : public QObject
    {
        Q_OBJECT
    public:
        explicit DataTest(QObject *parent,
                          SystemController& sysCtrl);

        void runTest();

    private:

        SystemController m_systemController;

        explicit DataTest(const DataTest& rhs) = delete;
        DataTest& operator= (const DataTest& rhs) = delete;
    };

}

然后是datatest.cpp的顶部：

#include "datatest.h"

#include "Model/systemcontroller.h"

namespace GUI
{
    DataTest::DataTest(QObject *parent,
                       SystemController& sysCtrl) :
        QObject(parent),
        m_systemController(sysCtrl) // FREAKS OUT HERE
    {
    }

Answer 1

在datatest.h中，您有以下成员变量

SystemController m_systemController;

由于变量是实例，您需要一个完整的包含，而不仅仅是一个前向声明。

如果只有指针或引用，只能使用前向声明，例如

SystemController* m_pSystemController;  // pointer
SystemController& m_rSystemController;  // reference

您还可以使用带有转发包含的智能指针

std::unique_ptr<SystemController> m_pSystemController;

变量的不完全类型 - 虽然我认为我有正确的声明？

1 个答案: