Assume I have this class (inherited from std::Vector, it's just an example)
#include <vector>
using namespace std;
template <class T>
class C : public vector<T> {
// I don't want to use static keyword
void transformation(T i) {
i *= 100;
}
public:
void method() {
for_each(this->begin(), this->end(), transformation);
}
};
int main() {
C<double> c;
for (int i=-3; i<4; ++i) {
c.push_back(i);
}
c.method();
}
How do I call for_each using class method inside class itself? I know I can use static keyword, but what is there any other way how to use a function object without using static?
I get this error message while compiling:
for_each.cc:21:55: error: cannot convert ‘C::transformation’ from type ‘void (C::)(double)’ to type ‘void (C::*)(double)’ for_each(this->begin(), this->end(), transformation);
I think I need to add .*
or ->*
somewhere but I can't find out where and why.
C++11 bind solution:
std::for_each(this->begin(), this->end(),
std::bind(&C::transformation, this, std::placeholders::_1));
C++11 lambda solution:
std::for_each(this->begin(), this->end(),
[this] (T& i) { transformation(i); });
C++14 generic lambda solution:
std::for_each(this->begin(), this->end(),
[this] (auto&& i) { transformation(std::forward<decltype(i)>(i)); });
C++98 bind1st+mem_fun solution:
std::for_each(this->begin(), this->end(),
std::bind1st(std::mem_fun(&C::transformation), this));
Note: this->begin()
and this->end()
calls are qualified with this->
only because in the OP's code they are member functions of a templated base class. As such, those names are primirarily searched in a global namespace. Any other occurrence of this
is mandatory.