Re: [Boost-users] for_each on boost::ptr_map

Subject: Re: [Boost-users] for_each on boost::ptr_map
From: Peter Barker (newbarker_at_[hidden])
Date: 2008-09-16 10:00:54

On Mon, Sep 15, 2008 at 9:20 PM, Robert Dailey <rcdailey_at_[hidden]> wrote:
> Hi,
>
> Is there a way I can use std::for_each() on a boost::ptr_map and have the
> functor object be given the *value* of each item iterated instead of a
> key/value pair like it does with std::map? Help is appreciated, thank you.

std::for_each() with std::map receives the pair so you need something
like the following to extract the value:

#include <algorithm>
#include <iostream>
#include <map>
#include <string>

#include <boost/bind.hpp>

class MyClass
{
public:
        MyClass(int x) : x_(x) {}
        int getX() const {return x_;}
private:
        int x_;
};

void func(MyClass* mc)
{
        std::cout << mc->getX() << std::endl;
}

int main()
{
        typedef std::map<std::string,MyClass*> MapType;
        MapType myPtrMap;

        std::string key1 = "Key1";
        std::string key2 = "Key2";
        myPtrMap.insert(std::make_pair(key1,new MyClass(1)));
        myPtrMap.insert(std::make_pair(key2,new MyClass(2)));
        std::for_each(myPtrMap.begin(),myPtrMap.end(),boost::bind(&func,boost::bind(&MapType::value_type::second,_1)));
}

Here's the same code working with ptr_map:

#include <algorithm>
#include <iostream>
#include <string>

#include <boost/bind.hpp>
#include <boost/ptr_container/ptr_map.hpp>

class MyClass
{
public:
        MyClass(int x) : x_(x) {}
        int getX() const {return x_;}
private:
        int x_;
};

void func(MyClass* mc)
{
        std::cout << mc->getX() << std::endl;
}

int main()
{
        typedef boost::ptr_map<std::string,MyClass> MapType;
        MapType myPtrMap;

        std::string key1 = "Key1";
        std::string key2 = "Key2";
        myPtrMap.insert(key1,new MyClass(1));
        myPtrMap.insert(key2,new MyClass(2));
        std::for_each(myPtrMap.begin(),myPtrMap.end(),boost::bind(&func,boost::bind(&MapType::value_type::second,_1)));
}

I hope that helps you out.

Regards,

Pete