OptionalValue.h

// This file is a part of the OpenSurgSim project.
// Copyright 2013, SimQuest Solutions Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef SURGSIM_DATASTRUCTURES_OPTIONALVALUE_H
#define SURGSIM_DATASTRUCTURES_OPTIONALVALUE_H

#include "SurgSim/Framework/Assert.h"

namespace SurgSim
{
namespace DataStructures
{

template <class T>
class OptionalValue
{
public:

    OptionalValue()  : m_hasValue(false)
    {
    }

    explicit OptionalValue(const T& value) : m_hasValue(true), m_value(value)
    {
    }

    OptionalValue(const OptionalValue& other) : m_hasValue(other.m_hasValue)
    {
        if (m_hasValue)
        {
            m_value = other.m_value;
        }
    }

    bool hasValue() const
    {
        return m_hasValue;
    }

    void invalidate()
    {
        m_hasValue = false;
    }

    void setValue(const T& val)
    {
        m_hasValue = true;
        m_value = val;
    }

    const T& getValue() const
    {
        SURGSIM_ASSERT(m_hasValue) << "Tried to fetch a value from an invalid OptionalValue";
        return m_value;
    }

    const T& operator*() const
    {
        SURGSIM_ASSERT(m_hasValue) << "Tried to fetch a value from an invalid OptionalValue";
        return m_value;
    }

    bool operator==(const OptionalValue<T>& rhs) const
    {
        if (m_hasValue == true && rhs.m_hasValue == true)
        {
            return m_value == rhs.m_value;
        }
        else
        {
            return m_hasValue == rhs.m_hasValue;
        }
    }


    bool operator==(const T& rhs) const
    {
        if (m_hasValue)
        {
            return m_value == rhs;
        }
        else
        {
            return false;
        }
    }

    bool operator!=(const OptionalValue<T>& rhs) const
    {
        return !(*this == rhs);
    }

    bool operator!=(const T& rhs) const
    {
        return !(*this == rhs);
    }

    OptionalValue& operator=(const OptionalValue& rhs)
    {
        m_hasValue = rhs.m_hasValue;
        if (m_hasValue)
        {
            m_value = rhs.m_value;
        }
        return *this;
    }

    OptionalValue& operator=(const T& rhs)
    {
        setValue(rhs);
        return *this;
    }

private:
    bool m_hasValue;
    T m_value;
};

}; // Datastructures
}; // SurgSim

#endif