關於C++ friend (沒看過這樣用template)

http://mtlung.blogspot.com/2008/06/inlcude-int-main-stdcout-hello-worldn.html

沒看過這樣用template

// Texture.h

class Texture { 

public: 

 friend class IResourceLoader; 

 uint width() const { return mWidth; } 

 uint height() const { return mHeight; } 

 

 // We declare a templated inner class here (but not defined yet)

 template<class> class PrivateAccessor; //看不懂@@

 

 private: 

 uint mWidth; 

 uint mHeight; 

};

 

class IResourceLoader {}; 

 

// JpegLoader.cpp

// Define Texture::PrivateAccessor here, access what ever you want

template<> //看不懂@@

class Texture::PrivateAccessor<jpegloader> {

public:

 static size_t& width(Texture& texture) {

  return texture.mWidth;

 }

 static size_t& height(Texture& texture) {

  return texture.mHeight;

 }

};

typedef Texture::PrivateAccessor<jpegloader> Accessor;

 

void JpegLoader::load() {

 // ... 

 Accessor::width(mTexture) = 128; // Ok! no problem

 Accessor::height(mTexture) = 128;

}