“运行时模板”(“run time templates”)

 我很确定答案是“你不能使用模板，你必须使用虚函数（动态多态）”，但似乎我必须复制很多代码，如果我去那条路线。 这是设置： 
 
 我目前有两个类，ColorImageSegmentation和GrayscaleImageSegmentation。 它们基本上是相同的，但有三个不同 - 它们在不同的类型（ColorImage和GrayscaleImage）上运行 - 一个参数，直方图的维度（3对1）是不同的 - PixelDifference函数根据图像类型而不同 
 
 如果我创建一个类 
 
template <TImageType>
class ImageSegmentation
{
};
 
 我会很好。 但是，我希望将此对象作为另一个类的成员： 
 
class MyMainClass
{
 ImageSegmentation MyImageSegmentation;
};
 
 但是用户需要确定MyImageSegmentation的类型（如果用户打开灰度图像，我想实例化MyImageSegmentation<GrayScaleType> 。同样对于彩色图像， MyImageSegmentation<ColorType> 。） 
 
 使用派生类，我可以存储指针，然后执行： 
 
class MyMainClass
{
 ImageSegmentation* MyImageSegmentation;
};

... user does something...
MyImageSegmentation = new ColorImageSegmentation;
 
 但是我怎么用模板做这样的事呢？ 问题是我有很多： 
 
typedef TImageType::HistogramType HistogramType;
typedef TImageType::PixelType PixelType;
 
 发生了一些事情，所以我不知道如何将它们转换为动态多态模型而不重复一大堆代码。 
 
 对不起，漫无目的......有人对我有什么建议吗？ 
 
 谢谢， 
 
 大卫 

I'm pretty sure the answer is "you can't use templates, you have to use virtual functions (dynamic polymorphism)", but it seems like I'd have to duplicate a lot of code if I went that route. Here is the setup:
 
I currently have two classes, ColorImageSegmentation and GrayscaleImageSegmentation. They do essentially the same thing, but there are three differences - they operate on different types (ColorImage and GrayscaleImage) - a parameter, the dimensionality of the histogram (3 vs 1) is different - The PixelDifference function is different based on the image type
 
If I create a class
 
template <TImageType>
class ImageSegmentation
{
};
 
I would be in good shape. However, I want to have this object as a member of another class:
 
class MyMainClass
{
 ImageSegmentation MyImageSegmentation;
};
 
But the user needs to determine the type of MyImageSegmentation (if the user opens a grayscale image, I want to instantiate MyImageSegmentation<GrayScaleType>. Likewise for a color image, MyImageSegmentation<ColorType>.)
 
With derived classes, I could store a pointer and then do:
 
class MyMainClass
{
 ImageSegmentation* MyImageSegmentation;
};

... user does something...
MyImageSegmentation = new ColorImageSegmentation;
 
but how would I do something like this with templates? The problem is I have a lot of:
 
typedef TImageType::HistogramType HistogramType;
typedef TImageType::PixelType PixelType;
 
sort of things going on, so I don't know how I would convert them to the dynamic polymorphic model without duplicating a whole bunch of code.
 
Sorry for the rambling... does anyone have any suggestions for me?
 
Thanks,
 
David

原文：https://stackoverflow.com/questions/4233300