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#pragma once
#include "PreConfig.h"
#include <memory>
namespace cru {
template <typename T>
class SelfResolvable;
template <typename T>
class ObjectResolver {
friend SelfResolvable<T>;
private:
ObjectResolver(const std::shared_ptr<T*>& resolver) : resolver_(resolver) {}
public:
ObjectResolver(const ObjectResolver&) = default;
ObjectResolver& operator=(const ObjectResolver&) = default;
ObjectResolver(ObjectResolver&&) = default;
ObjectResolver& operator=(ObjectResolver&&) = default;
~ObjectResolver() = default;
T* Resolve() const {
// resolver_ is null only when this has been moved.
// You shouldn't resolve a moved resolver. So assert it.
Expects(resolver_);
return *resolver_;
}
private:
std::shared_ptr<T*> resolver_;
};
template <typename T>
class SelfResolvable {
public:
SelfResolvable() : resolver_(new T*(static_cast<T*>(this))) {}
SelfResolvable(const SelfResolvable&) = delete;
SelfResolvable& operator=(const SelfResolvable&) = delete;
// Resolvers to old object will resolve to new object.
SelfResolvable(SelfResolvable&& other)
: resolver_(std::move(other.resolver_)) {
(*resolver_) = static_cast<T*>(this);
}
// Old resolvers for this object will resolve to nullptr.
// Other's resolvers will now resolve to this.
SelfResolvable& operator=(SelfResolvable&& other) {
if (this != &other) {
(*resolver_) = nullptr;
resolver_ = std::move(other.resolver_);
(*resolver_) = static_cast<T*>(this);
}
return *this;
}
virtual ~SelfResolvable() {
if (resolver_ != nullptr) (*resolver_) = nullptr;
}
ObjectResolver<T> CreateResolver() { return ObjectResolver<T>(resolver_); }
private:
std::shared_ptr<T*> resolver_;
};
} // namespace cru
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