c++实现扩展工厂类

基类
renader.h
#pragma once
#include
#include
using namespace std;
class IRenderer // 抽象基类, I作为前缀表明这是一个接口类
{
public:
virtual ~IRenderer() {}
virtual bool LoadScene(const string& filename) = 0; // 加载场景
virtual void SetViewportSize(int w, int h) = 0; // 设置视角大小
virtual void SetCameraPosition(double x, double y, double z) = 0; // 设置相机位置
virtual void SetLookAt(double x, double y, double z) = 0; // 设置视点
virtual void Render() = 0;
};

注册器RendererFactory.h
class RendererFactory
{
public:
typedef IRenderer*(CreateCallback)();
static void RegisterRenderer(const std::string& type, CreateCallback cb)//注册
{
renderers_[type] = cb;
};
static void UnregisterRenderer(const std::string& type)//删除
{
renderers_.erase(type);
};
static IRenderer CreateRenderer(const std::string& type)
{

	CallbackMap::iterator it = renderers_.find(type);
	if (it != renderers_.end()) {
		// 调用回调以构造此派生类的对象
		return (it->second)();
	}
	return NULL;
}

private:
typedef std::map CallbackMap;
static CallbackMap renderers_;
};
派生类UserRenderer .h
class UserRenderer : public IRenderer
{

public:
bool LoadScene(const std::string& filename) { return true; }
void SetViewportSize(int w, int h) {}
void SetCameraPosition(double x, double y, double z) {}
void SetLookAt() {}
void Render() { std::cout << “User Render” << std::endl; }
static IRenderer* Create()
{ return new Use
rRenderer(); } // 每个自定义renderer必须定义一个Create成员方法, 以向RendererFactory注册该创建自身对象的方法
};

使用
int main()
{
RendererFactory::RegisterRenderer(“User”, UserRenderer::Create)//注册
IRenderer p== RendererFactory::CreateRenderer(“user”);
p->Render();
}