flyweight.hpp File Reference

#include <functional>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <utility>

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Classes
struct	flyweight::default_creator< T, Args >
struct	flyweight::default_deleter< T >
struct	flyweight::autorelease_value< T, Flyweight, ArgTuple >
	Value wrapper that releases it back to the owning flyweight upon destruction. More...
class	flyweight::flyweight< T, Args >
class	flyweight::flyweight_refcounted< T, Args >

Functions
template<typename Fn , typename... Args>
auto	flyweight::detail::apply (Fn &&f, std::tuple< Args... > &&t)

Detailed Description

Single header with a templated implementation of the Flyweight design pattern

Example of asset management using flyweight objects:

#include "flyweight.hpp"
 
// 1. Declare your flyweight instance.
// The first template type is the value type.
// The rest are argument types used to create values.
// In this example, we're defining a resource manager for images.
flyweight::flyweight<Image, std::string> my_image_flyweight {
    // (optional) Pass a creator functor that will be called to create values.
    [](const std::string& image_name) {
        return LoadImage(image_name);
    },
    // (optional) Pass a deleter functor that will be called when values are released.
    [](Image& image) {
        UnloadImage(image);
    },
};
 
 
// 2. Get values from the flyweight.
// The first time the value will be created.
Image& image1 = my_image_flyweight.get("image1");
assert(my_image_flyweight.is_loaded("image1"));
// Subsequent gets will return the same reference to the same value.
Image& also_image1 = my_image_flyweight.get("image1");
assert(&image1 == &also_image1);
 
 
// 3. When you don't need values anymore, release them to the flyweight again.
my_image_flyweight.release("image1");
assert(!my_image_flyweight.is_loaded("image1"));
// Releasing a value that is not loaded is a harmless no-op.
my_image_flyweight.release("image that's not loaded");
 
 
// 4. (optional) Use RAII to automatically release a value by getting it with `get_autorelease`.
{
    auto autoreleased_image1 = my_image_flyweight.get_autorelease("image1");
    assert(my_image_flyweight.is_loaded("image1"));
    // Autoreleased values are simple wrappers to the original value reference.
    Image& image1 = autoreleased_image1;
}
// At this point "image1" was automatically released.
assert(!my_image_flyweight.is_loaded("image1"));