smart_ptr/shared_ptr_example.cpp

//  Boost shared_ptr_example.cpp  --------------------------------------------//

//  (C) Copyright Beman Dawes 2001. Permission to copy,
//  use, modify, sell and distribute this software is granted provided this
//  copyright notice appears in all copies. This software is provided "as is"
//  without express or implied warranty, and with no claim as to its
//  suitability for any purpose.

//  See http://www.boost.org for most recent version including documentation.

//  Revision History
//  21 May 01  Initial complete version (Beman Dawes)

//  The original code for this example appeared in the shared_ptr documentation.
//  Ray Gallimore pointed out that foo_set was missing a Compare template
//  argument, so would not work as intended.  At that point the code was
//  turned into an actual .cpp file so it could be compiled and tested.

#include <vector>
#include <set>
#include <iostream>
#include <algorithm>
#include <boost/smart_ptr.hpp>

//  The application will produce a series of
//  objects of type Foo which later must be
//  accessed both by occurrence (std::vector)
//  and by ordering relationship (std::set).

struct Foo
{ 
  Foo( int _x ) : x(_x) {}
  ~Foo() { std::cout << "Destructing a Foo with x=" << x << "\n"; }
  int x;
  /* ... */
};

typedef boost::shared_ptr<Foo> FooPtr;

struct FooPtrOps
{
  bool operator()( const FooPtr & a, const FooPtr & b )
    { return a->x > b->x; }
  void operator()( const FooPtr & a )
    { std::cout << a->x << "\n"; }
};

int main()
{
  std::vector<FooPtr>         foo_vector;
  std::set<FooPtr,FooPtrOps>  foo_set; // NOT multiset!

  FooPtr foo_ptr( new Foo( 2 ) );
  foo_vector.push_back( foo_ptr );
  foo_set.insert( foo_ptr );

  foo_ptr.reset( new Foo( 1 ) );
  foo_vector.push_back( foo_ptr );
  foo_set.insert( foo_ptr );

  foo_ptr.reset( new Foo( 3 ) );
  foo_vector.push_back( foo_ptr );
  foo_set.insert( foo_ptr );

  foo_ptr.reset ( new Foo( 2 ) );
  foo_vector.push_back( foo_ptr );
  foo_set.insert( foo_ptr );

  std::cout << "foo_vector:\n";
  std::for_each( foo_vector.begin(), foo_vector.end(), FooPtrOps() );
  
  std::cout << "\nfoo_set:\n"; 
  std::for_each( foo_set.begin(), foo_set.end(), FooPtrOps() );
  std::cout << "\n";

//  Expected output:
//
//   foo_vector:
//   2
//   1
//   3
//   2
//   
//   foo_set:
//   3
//   2
//   1
//
//   Destructing a Foo with x=2
//   Destructing a Foo with x=1
//   Destructing a Foo with x=3
//   Destructing a Foo with x=2
   
  return 0;
}