c++ - Qt:信号和槽 vs C++:消息传递

Question

我有两个类(class)

class Car
{
// class Car related methods
public:
setDriversName(QString);
private:
String driversName_;    // This information comes from class DriversName

//Must get the drivers name info, when a particular event in this object occurs;
}

class DriversName
{
//class DriversName related methods
String getDriversName();
private:
String driversName_;
}

所以，现在我想在两个类之间进行通信，更具体地说，我希望 Car 类在特定的时候从 DriversName 类中获取司机的名字 事件发生在 Car 对象中。

目前我有这两种方式，

C++ Message passing:

class Car
{
// class Car related methods
public:
setDriversNameObject(DriversName& );
setDriversName()
{
   driversName_ =  DriversName.getDriversName();
}

private:
DriversName driversName_;    // So after setting the Driverclass object, i can directly 
//access the driver's name, whenever the event occurs
String driversName_;
}

class DriversName
{
//class DriversName related methods
String getDriversName();

private:
DriversName driversName_;
}

或

Qt

In mainWindow class:

connect(carObject,eventHasOccured(),this,updateDriversName());


void MainWindow::updateDriversName()
{
    carObject->setDriversName(driversNameObject.getDriversName);
}

Class Car
{
    Q_OBJECT
    signals:
    emit eventHasOccured();

    public:
    setDriversNameObject(DriversName& );

    private:
    DriversName driversName_;              
}

Class DriversName
{
    Q_OBJECT

    String getDriversName();

    private:
    DriversName driversName_;    
}

这两种解决方案肯定会奏效。这是我的问题:

1) Is there any flaw in the above methods, with respect to OO principles.

2) Which is the most standard way this situation can be dealt with ?

3) is there any other better method to handle the given situation.

谢谢。

Answer 1

1) Is there any flaw in the above methods, with respect to OO principles.

第一种方法将 Car 方法与 DriversName 类紧密结合。

第二个将您的应用程序耦合到 Qt。如果你在整个应用程序中都使用它，那不是什么大问题，但应该考虑到这一点。此外，它将业务逻辑代码移动到主窗口类中，这可能不是一个好主意。

2) Which is the most standard way this situation can be dealt with ?

没有“一种明确的方法”可以做到这一点。只有更好和更坏的。

3) is there any other better method to handle the given situation.

对于“纯 C++”方法，您可以引入一个抽象接口(interface)来监听驱动程序名称更改(或者更一般地用于监听通用名称更改)。我在这里指的基本上是实现 Observer图案。简化的实现可以例如看起来像这样:

class NameChangeListener
{
public:
    virtual void onNameChange(std::string const & newName) =0;
};

// This assumes change is initiated in DriversName class - not sure if this is correct
// Your code doesn't show the actual triggering of the change
class DriversName
{
public:
// ... other stuff
    setNameChangeListener(NameChangeListener* ncl)
    {
        changeListener = ncl;
    }
    void setName(std::string const & newName)
    {
        // ... other stuff
        if (changeListener)
            changeListener->onNameChange(newName);
    }
private:
    // ..
    NameChangeListener* changeListener;
};

class Car: public NameChangeListener
{
public:
// ... other stuff
    void onNameChange(std::string const & newName) {
        driversName = newName;
    }
};

// somewhere outside:
Car c1;
DriversName n;
n.setNameChangeListener(c1);

对于 Qt 方法，最好引入一个额外的“Controller”类来封装这些关系，而不是直接在主窗口中进行。