c++ std::function 사용법

주의할 점은 std::function을 함수의 인자로 넘길 때

const를 붙여야 한다.

#include <iostream>
#include <functional>
 
class FunctionObj
{
public:
    void operator() (int i)
    {
        std::cout << "functionObj" << i << std::endl;
    }
 
};
 
void freeFunction(int i)
{
    std::cout << "freeFunction" << i << std::endl;
}
 
// 함수 포인터 전달
void runFunction(int i, void (*fnPtr)(int))
{
    (*fnPtr)(i);
}
// std::functional 사용
void runFunction_functional(int i, const std::function<void(int)>& fn)
{
    fn(i);
}
 
void runFunctions_vector(const std::vector<std::function<void(int)>> functions)
{
    int i = 0;
    for (const auto& fn : functions)
    {
        fn(++i);
    }
}
 
int main()
{
    freeFunction(10);
    // Function Pointer
    void(*fnPtr)(int);
    fnPtr = freeFunction;
    //(*fnPtr)(20);
 
    //runFunction(10, fnPtr);
    runFunction_functional(20, fnPtr);
 
    FunctionObj functionObj;
    functionObj(10);
 
    auto lambdaFn = [](int i)
    {
        std::cout << "lambdaFunction" << i << std::endl;
    };
 
    //lambdaFn(10);
 
    runFunction(10, lambdaFn);
 
    std::vector<std::function<void(int)>> functions;
    functions.emplace_back(freeFunction);
    functions.emplace_back(functionObj);
    functions.emplace_back(lambdaFn);
    runFunctions_vector(functions);
}