#include <iostream>
#include <string>
#include <map>
#include <exception>

#include "boost/shared_ptr.hpp"
#include "boost/pool/detail/singleton.hpp"

class Surface
{
public:
	Surface()
	{
		std::cout << "Loaded a surface." << std::endl;
	}
};

class Surface_Cache : public boost::details::pool::singleton_default<Surface_Cache>
{
public:
	typedef boost::shared_ptr<Surface> Surface_Ptr;
	typedef std::map<const std::string, Surface_Ptr> surface_cache;
	typedef surface_cache::iterator cache_it;

	Surface_Ptr Load_Surface(const std::string& file_name)
	{
		cache_it it = cache.find(file_name);

		if(it == cache.end())
		{ // Add surface.
			Surface_Ptr s(new Surface());
			cache.insert(std::make_pair(file_name, s));
			return s;
		}
		return it->second;
	}
private:
	surface_cache cache;
};

int main()
{
	return 0;
}

Quote:Any class with a non-throwing default constructor and non-throwing destructor

Quote:error C2248: 'boost::details::pool::singleton_default<T>::singleton_default' : cannot access private member declared in class 'boost::details::pool::singleton_default<T>'

Quote:Original post by Trenki
Why do you even want to use a singleton here? Is it an error if you ever instantiated another SurfaceCache? Probably not. If you really need global access to a SurfaceCache a global variable which gets initialized on program startup should be all you need.

Quote:Original post by Mybowlcut

Quote:Original post by Trenki
Why do you even want to use a singleton here? Is it an error if you ever instantiated another SurfaceCache? Probably not. If you really need global access to a SurfaceCache a global variable which gets initialized on program startup should be all you need.

Because there only ever needs to be on object that controls the loading of surfaces.. why would there ever need to be more than 1?

Quote:Original post by Mybowlcut

Quote:Original post by Trenki
Why do you even want to use a singleton here? Is it an error if you ever instantiated another SurfaceCache? Probably not. If you really need global access to a SurfaceCache a global variable which gets initialized on program startup should be all you need.

Because there only ever needs to be on object that controls the loading of surfaces.. why would there ever need to be more than 1?

class NonCopyable // or use boost::noncopyable{private:    // deliberately unimplemented    NonCopyable(const NonCopyable &);    NonCopyable&operator=(const NonCopyable &);};class Foo : NonCopyable {public:    Foo(/* ctor args */)};Foo::Foo(/* ctor args */){    static bool thereCanOnlyBeOne = true;    assert(thereCanOnlyBeOne);    thereCanOnlyBeOne = false;    // ...}

Quote:Original post by rip-off

Quote:Original post by Mybowlcut

Quote:Original post by Trenki
Why do you even want to use a singleton here? Is it an error if you ever instantiated another SurfaceCache? Probably not. If you really need global access to a SurfaceCache a global variable which gets initialized on program startup should be all you need.

Because there only ever needs to be on object that controls the loading of surfaces.. why would there ever need to be more than 1?

Unless the universe blows up by creating a second Foo, Foo should not be implemented as a Singleton.

Seriously. There are no real benefits to this pattern. Well, maybe when dealing with the C++ static order initialisation fiasco - but then again you should really try limit the amount of code that runs before main() anyway.

If you want to ensure there is only one instance of a particular class, there is a really easy way without corrupting the public interface:
*** Source Snippet Removed ***

Ignoring threading issues, this will give you peace of mind by ensuring any accidental creations are detected. Then, when your design changes and you need to have more than one of these objects, you will not have to change any more that the few lines in the constructor (and possibly no longer derive from the noncopyable class).

Quote:Original post by Mybowlcut
Should an assert or exception be used? I've only used exceptions. Could you please explain why you'd prefer an assert?

Quote:You say when my design changes, but I'm pretty sure it won't. There should only ever need to be one of this object.

Quote:Also, since this is a global now, how would I go about declaring it in other files? I've never had to use a global across files before haha.. :s