Re: member container and for_each with mem_fun

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 18 Oct 2010 07:58:54 -0400

Message-ID:

<daniel_t-530B8D.07585418102010@70-3-168-216.pools.spcsdns.net>

In article
<7b686e84-1e3e-4144-a036-4876189f0abc@b9g2000prc.googlegroups.com>,
cinsk <cinsky@gmail.com> wrote:

Hi,

If I have a class (that mimic some of STL's container) like this:

class Elem {
public:
  void prepare(); // do something on *this
  // ...
};

class Selector {
public:
  typedef vector<Elem *> container_type;
  typedef container_type::iterator iterator;

  iterator begin() { return cont_.begin(); }
  iterator end() { return cont_.end(); }

  void check_all();

private:
  prepare_elem(Elem *p); // do something on 'p'
  container_type cont_;
};

If I want to call prepare() for all elements in 'cont_', I could make
the following function:

void Selector::check_all() {
  for_each(cont_.begin(), cont_.end(), mem_fun(&Elem::prepare));
}

My question is, what if I want to call Selector::prepare_elem() for
all elements in 'cont_'? My initial approach won't compile:

void Selector::check_all() {
  for_each(cont_.begin(), cont_.end(),
mem_fun(&Selector::prepare_elem));
}

Is there anyway to use std::for_each() to call
Selector::prepare_elem()?

The problem with sending Selector::prepare_elem is that the objects in
the container are not Selector objects. Somehow you have to be able to
pass Elem objects to Selector::prepare_elem, how were you planing on
doing that?

Assuming:

void Selector::prepare_elem(Elem* e);

you could:

for_each(cont_.begin(), cont_.end(),
bind1st(mem_fun(&Selector::prepare_elem), this));