Undefined reference to static method

问题

This is probably something simple but I can't figure it out.

In my main.cpp I have:

Image image("/path/to/image.png");
int* h = ImageProcessor::dailyPrices(image);

And in my ImageProcessor.h I have:

//Maybe something is wrong with this? I am trying to forward declare.
namespace Magick
{
class Image;
}

class ImageProcessor {
public:
ImageProcessor();
virtual ~ImageProcessor();
static int* dailyPrices(const Magick::Image& abp_chart);
};

And in ImageProcessor.cpp I have

int* dailyPrices(const Image& abp_chart)
{

But upon attempt to compile I receive the following error in my main.cpp:

path/to/VendBot.cpp:17: undefined reference to `ImageProcessor::dailyPrices(Magick::Image const&)'

回答1:

You are missing the class name when defining the dailyPrices function:

int* ImageProcessor::dailyPrices(const Image& abp_chart)
//   ______________^ 
{
    // 
}

回答2:

You need to add ImageProcessor:: to your method definition:

int* ImageProcessor::dailyPrices(const Image& abp_chart)
     ^^^^^^^^^^^^^^^^

回答3:

dailyPrices needs to be in the ImageProcessor namespace:

int* ImageProcessor::dailyPrices(const Image& abp_chart)

来源：https://stackoverflow.com/questions/17428049/undefined-reference-to-static-method