对于COM对象使用ComPtr代替传统指针

对于COM对象来说使用传统指针比较麻烦，还要记得Release()防止内存泄漏，一不小心就会出现各种各样的问题。针对这种问题微软提供了对于COM对象的智能指针ComPtr，这里是官方文档https://github.com/Microsoft/DirectXTK/wiki/ComPtr

举个例子，原先的代码：

     ID3D11Buffer*                   m_pVertexBuffer;
     ID3D11Buffer*                   m_pIndexBuffer;
     ID3D11InputLayout*              m_pInputLayout;

     ID3DX11Effect*                  m_pFx;
     ID3DX11EffectTechnique*         m_pTechnique;
     ID3DX11EffectMatrixVariable*    m_pFxWorldViewProj;

 void HillsDemo::UnLoadContent()
 {
     if (m_pVertexBuffer) m_pVertexBuffer->Release();
     if (m_pIndexBuffer) m_pIndexBuffer->Release();
     if (m_pInputLayout) m_pInputLayout->Release();
     if (m_pTechnique) m_pTechnique->Release();
     if (m_pFx) m_pFx->Release();
 }

使用ComPtr的代码：

 Microsoft::WRL::ComPtr<ID3D11Buffer> m_pVertexBuffer;
 Microsoft::WRL::ComPtr<ID3D11Buffer> m_pIndexBuffer;
 Microsoft::WRL::ComPtr<ID3D11InputLayout> m_pInputLayout;

 Microsoft::WRL::ComPtr<ID3DX11Effect> m_pFx;
 ID3DX11EffectTechnique* m_pTechnique;
 ID3DX11EffectMatrixVariable* m_pFxWorldViewProj;

 void HillsDemo::UnLoadContent()
 {
     m_pVertexBuffer.Reset();
     m_pIndexBuffer.Reset();
     m_pInputLayout.Reset();
     m_pFx.Reset();
     m_pTechnique = nullptr;
     pFxWorldViewProj = nullptr;
 }