模板扣失敗

Question

任何人都可以解釋爲什麼這不起作用：

#include "itkCovariantVector.h" 
#include "itkImage.h" 

template <typename TComponent, int NumberOfComponents> 
void FillImage(itk::Image<itk::CovariantVector<TComponent, 
NumberOfComponents>, 2>* const image, 
       itk::Image<itk::CovariantVector<TComponent, 
NumberOfComponents>, 2>* const output) 
{ 
    std::cout << "Works." << std::endl; 
} 

int main(int, char* []) 
{ 
    typedef itk::Image<itk::CovariantVector<float, 3u>, 2u> ImageType; 

    ImageType::Pointer imageSmartPointer = ImageType::New(); 
    ImageType* image = imageSmartPointer.GetPointer(); 
    FillImage(image, image); 
    return 0; 
} 
/* 
no matching function for call to ‘FillImage(ImageType*&, ImageType*&)’ 
note: candidate is: 
template<class TComponent, int NumberOfComponents> void 
FillImage(itk::Image<itk::CovariantVector<TComponent, 
NumberOfComponents>, 2u>*, itk::Image<itk::CovariantVector<TComponent, 
NumberOfComponents>, 2u>*) 
*/ 

的那些類模板的定義是：http://www.itk.org/Doxygen/html/classitk_1_1CovariantVector.html http://www.itk.org/Doxygen/html/classitk_1_1Image.html

我創建了非ITK類相同的情況下，它工作正常：

#include <iostream> 

template <typename TPixel, int Dimensions> 
struct Image 
{ 
}; 

template <typename TComponent, int NumberOfComponents> 
struct Vector 
{ 
}; 

template <typename TComponent, int NumberOfComponents> 
void FillImage(Image<Vector<TComponent, NumberOfComponents>, 2 >* const image, 
       Image<Vector<TComponent, NumberOfComponents>, 2 >* const output) 
{ 
    std::cout << "Works." << std::endl; 
} 

int main(int, char* []) 
{ 
    typedef Image<Vector<float, 3>, 2 > ImageType; 

    ImageType* image = new ImageType; 
    FillImage(image, image); 
    delete image; 
    return 0; 
} 

誰能解釋可能是什麼區別？

Answer 1

問題是我必須將簽名從<int NumberOfComponents>更改爲<unsigned int NumberOfComponents>，因此它符合ITK類的定義。

#include <iostream> 

template <typename TPixel, int Dimensions> 
struct Image 
{ 
}; 

// The deduction works with this 
// template <typename TComponent, int NumberOfComponents> 
// struct Vector 
// { 
// }; 

// The deduction does NOT work with this (unsigned int vs int above) 
template <typename TComponent, unsigned int NumberOfComponents> 
struct Vector 
{ 
}; 

template <typename TComponent, int NumberOfComponents> 
void FillImage(Image<Vector<TComponent, NumberOfComponents>, 2 >* const image, 
       Image<Vector<TComponent, NumberOfComponents>, 2 >* const output) 
{ 
    std::cout << "Works." << std::endl; 
} 

int main(int, char* []) 
{ 
    typedef Image<Vector<float, 3>, 2 > ImageType; 

    ImageType* image = new ImageType; 
    FillImage(image, image); 
    return 0; 
}