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65 lines
2.0 KiB
65 lines
2.0 KiB
#ifndef ENTT_RESOURCE_LOADER_HPP
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#define ENTT_RESOURCE_LOADER_HPP
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#include <memory>
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#include "fwd.hpp"
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namespace entt {
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/**
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* @brief Base class for resource loaders.
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*
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* Resource loaders must inherit from this class and stay true to the CRTP
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* idiom. Moreover, a resource loader must expose a public, const member
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* function named `load` that accepts a variable number of arguments and returns
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* a shared pointer to the resource just created.<br/>
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* As an example:
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*
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* @code{.cpp}
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* struct my_resource {};
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*
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* struct my_loader: entt::resource_loader<my_loader, my_resource> {
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* std::shared_ptr<my_resource> load(int) const {
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* // use the integer value somehow
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* return std::make_shared<my_resource>();
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* }
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* };
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* @endcode
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*
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* In general, resource loaders should not have a state or retain data of any
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* type. They should let the cache manage their resources instead.
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*
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* @note
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* Base class and CRTP idiom aren't strictly required with the current
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* implementation. One could argue that a cache can easily work with loaders of
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* any type. However, future changes won't be breaking ones by forcing the use
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* of a base class today and that's why the model is already in its place.
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*
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* @tparam Loader Type of the derived class.
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* @tparam Resource Type of resource for which to use the loader.
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*/
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template<typename Loader, typename Resource>
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class resource_loader {
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/*! @brief Resource loaders are friends of their caches. */
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friend class resource_cache<Resource>;
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/**
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* @brief Loads the resource and returns it.
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* @tparam Args Types of arguments for the loader.
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* @param args Arguments for the loader.
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* @return The resource just loaded or an empty pointer in case of errors.
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*/
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template<typename... Args>
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std::shared_ptr<Resource> get(Args &&... args) const {
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return static_cast<const Loader *>(this)->load(std::forward<Args>(args)...);
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}
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};
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}
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#endif // ENTT_RESOURCE_LOADER_HPP
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