c++ - C++：如何创建函子

Question

我正在尝试像这样创建一个仿函数：

struct STFRandomTreeFunction
{
    typedef double (*function_ptr)(const TrainingDataPoint& data, boost::unordered_map<std::string, cv::Mat>& preloaded_images);
};


struct STFRandomTreeFunctor
{
private:
    boost::unordered_map<std::string, cv::Mat> *image_cache;
    STFRandomTreeFunction::function_ptr function;
    std::string function_id;

public:
    STFRandomTreeFunctor(boost::unordered_map<std::string, cv::Mat>& cache, STFRandomTreeFunction::function_ptr function_ptr, std::string function_id){
        image_cache = &cache;
        this->function = function;
        this->function_id = function_id;
    }

    std::string get_function_id(){
        return function_id;
    }

    double operator()(const TrainingDataPoint& data_point){
        return function(data_point, *image_cache);
    }
};

我正在尝试运行以下代码：

double something(const TrainingDataPoint& a, unordered_map<string, Mat>& cache){
    return 5;
}


int main(int argc, char* argv[]) {

    unordered_map<string, Mat> cache;

    STFRandomTreeFunctor functor = STFRandomTreeFunctor(cache, something, "id");

    TrainingDataPoint d = TrainingDataPoint(1,2,"", ImagePoint(1,2), ImagePoint(1,2), "");

    double value  = functor(d);

    cout << "Value is " << value << endl;
}

但是，我没有得到任何输出。似乎抛出了一些异常，但是 eclipse 并没有向我显示一个，而只是显示该程序已终止。

有任何想法吗？

Answer 1

在构造函数中STFRandomTreeFunctor

this->function = function;

那是自我分配。我假设您打算这样做：

this->function = function_ptr;