将clsid与运行时类关联起来,以便在外部DLL中延迟绑定运行时类。
以下是一个示例,展示如何在Windows Runtime Component中使用winrt::create_instance函数来动态创建COM对象:
// HelloWorldComponent.h
namespace HelloWorldComponent
{
    public ref class HelloWorld sealed
    {
    public:
        void SayHello();
    };
}
// HelloWorldComponent.cpp
#include "pch.h"
#include "HelloWorldComponent.h"
using namespace winrt;
// 获取运行时类
namespace
{
    // 此类包装了Windows.Foundation.IInspectable接口,提供了一个方便的RefPtr/NULL检查的构造函数
    class inspectable : public implements
    {
    public:
        inspectable(void* p = nullptr) : m_ptr(p) {}
        Windows::Foundation::IInspectable get() const { return m_ptr; }
    private:
        Windows::Foundation::IInspectable m_ptr;
    };
    // 获取指定CLSID对应的运行时对象
    void get_runtime_object(winrt::hstring const& clsid, inspectable& object)
    {
        // 调用Windows API来获取IActivationFactory
        winrt::hstring typeName(L"");
        auto hr = ::CLSIDFromProgID(clsid.c_str(), &object.get_object()->m_pObjectIID);
        if (hr != S_OK)
        {
            winrt::throw_hresult(hr);
        }
        winrt::check_hresult(::CoGetClassObject(__uuidof(Windows::Foundation::IActivationFactory),
                                                CLSCTX_INPROC_SERVER,
                                                nullptr,
                                                IID_PPV_ARGS(&object)));
        object.get_object()->m_pObject->ActivateInstance(&object.get());
    }
}
namespace HelloWorldComponent
{
    void HelloWorld::SayHello()
    {
        // 动态获取COM对象的CLSID
        winrt::hstring clsid(L"HelloWorldCOMServer.HelloWorldObject");
        inspectable instance;
        get