好的,我看了很多“无法推断模板参数”的问题,但似乎没有一个符合我的情况 - 或者我不理解答案...
有一个问题,我觉得它朝着正确的方向发展,但我没能从中提取出解决我的问题的方法。
我的头文件中精简后的代码如下:
template<typename T>
class TemplateProblem
{
public:
// Do I really need this or did I miss something from the STL?
template<typename Tin, typename Tout>
struct UnaryFunction : public std::unary_function<Tin, Tout>
{
virtual Tout operator()(Tin input) = 0;
};
template<typename Tin, typename Tout>
struct StaticCast : public UnaryFunction<Tin, Tout>
{
virtual Tout operator()(Tin input)
{
return static_cast<Tout>(input);
}
};
private:
T * const _data;
T const _bias;
template<typename Tin>
void Init(Tin * data, int length, UnaryFunction<Tin, T> mapper, Tin bias);
public:
template<typename Tin>
TemplateProblem(Tin * data, int length, Tin bias = Tin());
template<typename Tin>
TemplateProblem(Tin * data, int length, UnaryFunction<Tin, T> mapper, Tin bias = T());
};
template<typename T>
template<typename Tin>
void TemplateProblem<T>::Init(Tin * data, int length, UnaryFunction<Tin, T> mapper, Tin bias)
{
T mappedBias = mapper(bias);
for (int i = 0; i < length; i++)
{
_data[i] = data[i] + mappedBias;
}
}
template<typename T>
template<typename Tin>
TemplateProblem<T>::TemplateProblem(Tin * data, int length, UnaryFunction<Tin, T> mapper, Tin bias = T())
: _data(new T[length]), _bias(bias)
{
Init(data, length, mapper, bias);
}
template<typename T>
template<typename Tin>
TemplateProblem<T>::TemplateProblem(Tin * data, int length, Tin bias = T())
: _data(new T[length]), _bias(bias)
{
StaticCast<Tin, T> cast;
Init(data, length, cast, bias);
}
我是这样实例化它的:
unsigned char pixels[] = {23, 42, 65, 97};
TemplateProblem<int> tp(pixels, 4);
我从VS2012中得到了这些消息:
Error 1 error C2784: 'void TemplateProblem<T>::Init(Tin *,int,TemplateProblem<T>::UnaryFunction<Tin,T>,Tin)' : could not deduce template argument for 'TemplateProblem<T>::UnaryFunction<Tin,T>' from 'TemplateProblem<T>::StaticCast<Tin,Tout>' ...\templateproblem.h 62 1 TemplateProblem
Error 2 error C2893: Failed to specialize function template 'void TemplateProblem<T>::Init(Tin *,int,TemplateProblem<T>::UnaryFunction<Tin,T>,Tin)' ...\templateproblem.h 62 1 TemplateProblem
根据这个答案的建议,如果我将这两个struct
从class
中移出,同样会出现该错误。