JUCE/modules/juce_core/containers/juce_ScopedValueSetter.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Helper class providing an RAII-based mechanism for temporarily setting and
    then re-setting a value.

    E.g. @code
    int x = 1;

    {
        ScopedValueSetter setter (x, 2);

        // x is now 2
    }

    // x is now 1 again

    {
        ScopedValueSetter setter (x, 3, 4);

        // x is now 3
    }

    // x is now 4
    @endcode

    @tags{Core}
*/
template <typename ValueType>
class ScopedValueSetter
{
public:
    /** Creates a ScopedValueSetter that will immediately change the specified value to the
        given new value, and will then reset it to its original value when this object is deleted.
    */
    ScopedValueSetter (ValueType& valueToSet,
                       ValueType newValue)
        : value (valueToSet),
          originalValue (valueToSet)
    {
        valueToSet = newValue;
    }

    /** Creates a ScopedValueSetter that will immediately change the specified value to the
        given new value, and will then reset it to be valueWhenDeleted when this object is deleted.
    */
    ScopedValueSetter (ValueType& valueToSet,
                       ValueType newValue,
                       ValueType valueWhenDeleted)
        : value (valueToSet),
          originalValue (valueWhenDeleted)
    {
        valueToSet = newValue;
    }

    ~ScopedValueSetter()
    {
        value = originalValue;
    }

private:
    //==============================================================================
    ValueType& value;
    const ValueType originalValue;

    JUCE_DECLARE_NON_COPYABLE (ScopedValueSetter)
};

} // namespace juce