我正在寻求关于我目前的方法是否有意义的建议.如果没有,我想建议一些类型的设计模式,而不是用来取代我目前的直觉.
我的前提是我有一台相机,需要一个CameraLink或CoaXPress电缆接口连接到PC的帧抓取卡.必须使用帧抓取卡控制相机和计算机之间的所有通信和数据传输,因此这两个物理硬件对象之间的耦合非常紧密.
我的问题是我想创建一个“Camera”对象(用于GUI),它具有一个“FrameGrabber”卡对象,用于获取数据和发送/接收命令和数据.但是,我有许多不同类型的不同帧抓取卡.让我们称它们为CoaxGrabberA,CoaxGrabberB,LinkGrabberA和LinkGrabberB.与LinkGrabbers相比,CoaxGrabbers需要一组不同的初始化,设置器和getter参数.
因此,我认为我需要使用两个级别的继承,但是从我读过的所有内容来看,应该很少使用继承,并且应该优先考虑组合.因此,我非常怀疑我的设计决策,并寻求某种更好的设计.这是一些半生不熟的代码的例子.它有点冗长,但重要的部分是CoaxGrabberA,CoaxGrabberB,LinkGrabberA和LinkGrabberB是FrameGrabber的孙子孙女的概念,它必须可供Camera使用.其他一切都是为了填写您可能需要的细节.
我的目标是在运行时选择我想用于Camera对象的任何framegrabber(任何make / model / interface).此外,我想轻松访问该孙子framegrabber类型所特有的所有成员函数,以在运行时修改硬件的行为.
我的问题是“是否有一个特定的设计模式来匹配我不知道的问题,这将使我的生活比使用我天真,直观的方法更容易”
//-----------------------------------------
// Parent Class
//=========================================
class FrameGrabber {
public:
virtual void sendCommandString(std::string cmd) = 0;
virtual void startAcquisition() = 0;
virtual void stopAcquisition() = 0;
};
//-----------------------------------------
// Children Classes
//=========================================
class CoaxGrabber : FrameGrabber {
public:
//functions unique to coax grabbers
virtual void setCommAddress(int commAddress) = 0;
virtual void setStatusPort(int statusPort) = 0;
//functions universal to all grabbers
virtual void sendCommandString(std::string cmd) = 0;
virtual void startAcquisition() = 0;
virtual void stopAcquisition() = 0;
protected:
int _commAddress;
int _statusPort;
};
class LinkGrabber : FrameGrabber {
public:
//functions unique to link grabbers
virtual void setBaudRate(int baudRate) = 0;
virtual void setNumChannels(int numChannels) = 0;
//functions universal to all grabbers
virtual void sendCommandString(std::string cmd) = 0;
virtual void startAcquisition() = 0;
virtual void stopAcquisition() = 0;
protected:
int _baudRate;
int _numChannels;
};
//-----------------------------------------
// Grandchildren Classes
//=========================================
class CoaxGrabberA : public CoaxGrabber {
//identical public members as CoaxGrabber
//different implementation using
//different low-level API, ex: BitFlow
}
class CoaxGrabberB : public CoaxGrabber {
//identical public members as CoaxGrabber
//different implementation using
//different low-level API, ex: Kaya
}
class LinkGrabberA : public LinkGrabber {
//identical public members as LinkGrabber
//different implementation using
//different low-level API, ex: NationalInstruments
}
class LinkGrabberB : public LinkGrabber {
//identical public members as LinkGrabber
//different implementation using
//different low-level API, ex: Imperx
}
//-----------------------------------------------------
// Finally, my Camera object, nothing too interesting here
//=====================================================
class Camera {
public:
Camera() {
_frameGrabber = NULL;
}
~Camera() {
delete _frameGrabber;
}
void setGrabber(FrameGrabber* newGrabber)
{
delete _frameGrabber;
_frameGrabber = newGrabber;
}
void startAcquisition() {
_frameGrabber.startAcquisiton();
}
void stopAcquisition() {
_frameGrabber.stopAcquisition();
}
int setSensitivity(int sens) {
_frameGrabber.sendCommandString("sens=" + std::to_string(sens));
}
private:
FrameGrabber* _frameGrabber;
};
//-----------------------------------------
// This is why I don't like my Camera object
// the actual end-user interface smells
//=========================================
class CameraGui : QMainWindow
{
public:
void setGrabberType(int type);
void setCoaxGrabberCommAddress(int address);
void setLinkGrabberBaudRate(int rate);
CameraSystem _myCamera;
CoaxGrabber* _myCoaxGrabber;
LinkGrabber* _myLinkGrabber;
};
//---------------------------------------------------------------
//This function smells to me, but I cannot think of any other way
//of course, int type will be enum in actual program.
//===============================================================
void CameraGui::setGrabberType(int type) {
switch (type) {
case 0:
delete _myCoaxGrabber;
_myCoaxGrabber = new CoaxGrabberA();
_myCamera.setGrabber(&_myCoaxGrabber);
break;
case 1:
delete _myCoaxGrabber;
_myCoaxGrabber = new CoaxGrabberB();
myCamera.setGrabber(&_myCoaxGrabber));
break;
case 2:
delete _myLinkGrabber;
_myLinkGrabber = new LinkGrabberA();
_myCamera.setGrabber(&_myLinkGrabber);
break;
case 3:
delete _myLinkGrabber;
_myLinkGrabber = new LinkGrabberB();
_myCamera.setGrabber(&_myLinkGrabber);
break;
}
}
//---------------------------------------------------------------
// this method of setting parameters also smells to me,
// since this data is linked to the Camera object, which
// will have no way of knowing whether the state of its
// framegrabber changed... furthermore, if I change framegrabbers,
// none of the parameter settings (state) will be remembered.
// the user will need to set them all over again.
// the only way I know to circumvent this is to allocate memory for
// every type of framegrabber, and broadcast all state changes to
// all applicable parent grabbers, which will reside in permanent
// memory until the application closes.
//===============================================================
void CameraGui::setCoaxGrabberCommAddress(int address) {
if(myCoaxGrabber != NULL) {
myCoaxGrabber->setCommAddress(address);
}
}
//likewise smell
void CameraGui::setLinkGrabberBaudRate(int rate) {
if(myLinkGrabber != NULL) {
myLinkGrabber->setBaudRate(rate);
}
}
任何和所有的建议将不胜感激.长话短说,我对OO设计模式知之甚少,但这感觉就像一个解决的问题,我觉得我正在重新发明轮子.是否有更好,更成熟的方式来实现我想要做的事情？
最佳答案 您的设计模式称为“工厂”,继承没有任何问题(
https://en.wikipedia.org/wiki/Factory_method_pattern)
在继承和聚合之间选择时我们应该使用的经验法则：
>如果某事反映“是”关系(例如CoaxGrabber是FrameGrabber)使用继承.
>如果某事反映出“有”关系(例如CameraGui有FrameGrabber),则使用聚合.
我建议使用智能指针(例如std :: shared_ptr)而不是new并删除当前使用的内容将使代码更易于管理且不易出错.
在这种情况下：
class Camera {
public:
CameraSystem() {} // don't need explicit initialization
~CameraSystem() {} // resource in shared_ptr will be deleted automatically
void setGrabber(const std::shared_ptr<FrameGrabber>& newGrabber)
{
_frameGrabber = newGrabber;
}
void startAcquisition() {
_frameGrabber->startAcquisiton(); // note -> instead of .
}
// ....
private:
std::shared_ptr<FrameGrabber> _frameGrabber;
};
如果使用工厂：
void CameraGui::setGrabberType(int type) {
_myCamera.setGrabber(GrabberFactory::createGrabber(type));
}
class GrabberFactory {
public:
std::shared_ptr<FrameGrabber> createGrabber(int type) {
switch (type) {
case GrabberTypeCoaxA: return {new CoaxGrabberA()};
case GrabberTypeCoaxB: return {new CoaxGrabberB()};
default: throw std::invalid_argument("Invalid grabber type");
}
}
};
