C++：2.工厂模式

工厂模式主要解决，同一类接口，不同厂家有不同实现这类问题。

以业务集成相机sdk为例，相机常用到的功能有打开相机、读取流、关闭流、设置相机参数等。但不同厂家sdk实现方式不一样，如果不用工厂模式，那相同的业务代码，可能要写很多份。使用后，整体代码变得简洁，耦合性好。下面举例说明。

1.抽象相机基类

基类中通常包含两类接口，一类是通用接口，这类接口和相机厂家无关，但相机创建时候又都会用到。另一类是纯虚函数接口，这类接口就是相机相关操作的抽象，如打开相机等。

基类头文件

#ifndef _ICAMERA_H_ #define _ICAMERA_H_ #include <string> #include <map> class ICamera { public: ICamera(std::string cameraName) :name(cameraName) {}; /** * @brief 加载本地图片，仿真使用 * @param cameraName * @param simPicDir */ ICamera(std::string cameraName, std::string picDir); virtual ~ICamera() = default; /*************************相机厂家重写*************************/ /** * @brief 相机初始化 * @return */ virtual void init(CameraManagePara cmPara) = 0; /** * @brief 设置相机参数 * @param para * @return */ virtual bool setParameter(CameraThreadPara para) = 0; /** * @brief 相机在线状态 * @return */ virtual bool isOnline() = 0; /** * @brief 句柄是否有效 * @return */ virtual bool isValidHandle() = 0; /** * @brief 关闭相机 */ virtual void close() = 0; /** * @brief 关闭流 * @param */ virtual void stopGrab() = 0; /*************************基类通用接口-厂家不需要实现*************************/ /** * @brief 获取相机名称 * @return */ std::string getCameraName(); /** * @brief 可以抽取出来的通用逻辑 * @return */ void commonFun(std::string picDir); public: /** * @brief 通用成员变量 */ uint64_t frameTime = 0; uint64_t frameId = 0; /** * @brief 相机名称 */ std::string name; }; #endif // !_ICAMERA_H_

基类源文件

#include "ICamera.h" ICamera::ICamera(std::string cameraName, std::string picDir) { name = cameraName; commonFun(picDir); } std::string ICamera::getCameraName() { return name; } void ICamera::commonFun(std::string picDir) { //业务逻辑 }

2.具体相机子类

这里只举例一个厂家，如果多个厂家，写多个子类就行。

头文件

#ifndef _DSCAMERA_H_ #define _DSCAMERA_H_ #include "ICamera.h" #include "DVPCamera.h" class DSCamera : public ICamera { public: ~DSCamera() override { close(); } DSCamera(std::string cameraName, std::string simPicDir) : ICamera(cameraName, simPicDir) {} /** * @brief 相机初始化 * @return */ virtual void init(CameraManagePara cmPara) override; /** * @brief 设置相机参数 * @param para * @return */ virtual bool setParameter(CameraThreadPara para) override; /** * @brief 相机在线状态 * @return */ virtual bool isOnline() override; /** * @brief 句柄是否有效 * @return */ virtual bool isValidHandle() override; /** * @brief 关闭相机 */ virtual void close() override; /** * @brief 关闭流 * @param */ virtual void stopGrab() override; private: //bool isValidHandle(); void connect(CameraManagePara cmPara); //相机原生句柄 dvpHandle handle; }; #endif // !_DSCAMERA_H_

源文件

#include "DSCamera.h" dvpInt32 dSCameraCallBack(dvpHandle handle, dvpStreamEvent event, void* pContext, dvpFrame* pFrame, void* pBuffer) { DSCamera* pThis = (DSCamera*)pContext; //基类通用变量 pThis->frameId = pFrame->uFrameID; //回调取图 cv::Mat mat = cv::Mat(pFrame->iHeight, pFrame->iWidth, CV_8UC3, (uchar*)pBuffer, pFrame->iWidth * 3).clone(); return 0; } void DSCamera::init(CameraManagePara cmPara) { connect(cmPara); } bool DSCamera::setParameter(CameraThreadPara para) { dvpStatus status; //关闭流 status = dvpStop(handle); //设置相机参数等等 //开启流 status = dvpStart(handle); return true; } bool DSCamera::isOnline() { if (!isValidHandle()) return false; dvpStatus status; bool online = false; status = dvpIsOnline(handle, &online); if (status != DVP_STATUS_OK) { LOG(ERROR) << " get online status error " << std::endl; return false; } return online; } void DSCamera::close() { //关闭视频流 dvpStatus status = dvpStop(handle); //关闭相机 dvpStatus status1 = dvpClose(handle); } bool DSCamera::isValidHandle() { bool isValid = false; dvpStatus status = dvpIsValid(handle, &isValid); if (status != DVP_STATUS_OK) { return false; } return isValid; } void DSCamera::stopGrab() { dvpStatus status = dvpStop(handle); } void DSCamera::connect(CameraManagePara cmPara) { dvpStatus status; status = dvpOpenByUserId(name.c_str(), OPEN_NORMAL, &handle); //设置相机属性-略 //设置回调 status = dvpRegisterStreamCallback(handle, dSCameraCallBack, STREAM_EVENT_FRAME_THREAD, this); }

3.抽象工厂

通过工厂来创建具体子类对象。

#ifndef _ICAMERAFACTORY_H_ #define _ICAMERAFACTORY_H_ #include "ICamera.h" #include "DSCamera.h" #include "DHCamera.h" #include "MDWSCamera.h" class ICameraFactory { public: virtual ~ICameraFactory() = default; // 创建对应厂商相机实例 virtual ICamera* createCamera(std::string cameraName, std::string picPath) = 0; }; class DSCameraFactory : public ICameraFactory { public: ICamera* createCamera(std::string cameraName, std::string picPath) override { return new DSCamera(cameraName, picPath); } }; class DHCameraFactory : public ICameraFactory { public: ICamera* createCamera(std::string cameraName, std::string picPath) override { return new DHCamera(cameraName, picPath); } }; class MDWSCameraFactory : public ICameraFactory { public: ICamera* createCamera(std::string cameraName, std::string picPath) override { return new MDWSCamera(cameraName, picPath); } }; class CameraFactoryManager { public: // 根据相机类型创建相机实例 static ICamera* createCamera(const std::string& camType, const std::string& camName, const std::string& picPath) { if (camType == "DS") { return DSCameraFactory{}.createCamera(camName, picPath); } else if (camType == "DH") { return DHCameraFactory{}.createCamera(camName, picPath); } else if (camType == "MDWS") { MDWSCameraFactory factory; return MDWSCameraFactory{}.createCamera(camName, picPath); } else { throw std::runtime_error("unsupported camera type: " + camType); } } }; #endif // !_ICAMERAFACTORY_H_