Cached.h

// WARNING: Changes to this file must be contributed back to Sawyer or else they will
//          be clobbered by the next update from Sawyer.  The Sawyer repository is at
//          https://github.com/matzke1/sawyer.
 
 
 
 
#ifndef Sawyer_Cached_H
#define Sawyer_Cached_H
 
#include <Sawyer/Sawyer.h>
#include <Sawyer/Optional.h>
#include <boost/serialization/access.hpp>
#include <boost/serialization/nvp.hpp>
 
namespace Sawyer {
 
template<typename T>
class Cached {
public:
    typedef T Value;
 
private:
    mutable Sawyer::Optional<Value> value_;
 
private:
    friend class boost::serialization::access;
 
    template<class S>
    void serialize(S &s, const unsigned /*version*/) {
        s & BOOST_SERIALIZATION_NVP(value_);
    }
    
public:
    bool isCached() const {
        return bool(value_);
    }
 
    void clear() const {                                // const is intended
        value_ = Sawyer::Nothing();
    }
 
    const Value& get() const {
        return value_.get();
    }
    Value& get() {
        return value_.get();
    }
    const Sawyer::Optional<Value>& getOptional() const {
        return value_;
    }
 
    void set(const Value &x) const {                    // const is intentional
        value_ = x;
    }
    const Cached& operator=(const Value &x) const {     // const is intentional
        value_ = x;
        return *this;
    }
};
 
} // namespace
 
#endif