using std::transform for calling object's function

Question

Suppose I have a vector of shared pointers of objects of class A. I want to collect all the return values of method A::foo for all of the A objects and store them in some container, say another vector. Can this be done with std::transform or std::for_each and std::bind or some boost function ?

class A {

  public:
  string foo(int p);

};

std::vector<shared_ptr<A>> vec;

Answer 1

std::transform is fine for this:

std::vector<std::string> string_vec;
const int magic_number = 42;
std::transform(std::begin(vec),
              std::end(vec),
              std::back_inserter(string_vec),
              [magic_number](std::shared_ptr<A> a){ return a->foo(magic_number); } );

Obviously, you need to figure out which int you want to pass to A::foo(int).

In C++03, you can replace the lambda by a functor or function:

struct get_foo
{
  get_foo(int n) : n_(n) {}
  bool operator() (std::shared_ptr<A> a) const { return a->foo(n); }
private:
  int n_;
};

const int magic_number = 42;
std::vector<std::string> string_vec;
std::transform(std::begin(vec),
              std::end(vec),
              std::back_inserter(string_vec),
              get_foo(magic_number));