Niklas Niklas - 1 month ago 9
C++ Question

c++ pass data source function as parameter

I have a static function:

void E::createEP(std::list<double>* ret, double length, double (*getHeight)(double)) {
// magic
double sampleIntervall = //from magic

double dist = 0;
while (length - dist > -0.1) {
ret->push_back(dist, (*getHeight)(dist));
dist += sampleIntervall;
}
}


In different calls I have two different functions to pass as getHeight():


  • A function in a database wrapper class which is not static

  • A function within the same Object of type
    E
    as
    createEP()
    (for "recreating" with different parameters), which needs to access Elements fields and can thus not be static, either.



Is it somehow possible to pass non-static functions as parameters to a static function?

If not, what would be the most elegant alternative? I don't want to duplicate the entire code in
createEP()
.

Answer

What you can use is a std::function. It will wrap a callable type be that a function, member function, object with an overloaded function operator. You just need to supply the signature to use. So in you case you would have

void E::createEP(std::list<double>* ret, double length, std::function<double(double)> getHeight) 

Then to bind the member function with the object you want to call it on you can use a lambda like

[&](double val){ return object.FunctionName(val); }

or std::bind like

std::bind(&ClassName::FunctionName, &object)
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