/thirdparty/qxt/qxtweb-standalone/qxtweb/qxtnullable.h
http://github.com/tomahawk-player/tomahawk · C Header · 146 lines · 61 code · 18 blank · 67 comment · 1 complexity · ec6ea087de71698e89c9d50b2092c823 MD5 · raw file
- /****************************************************************************
- **
- ** Copyright (C) Qxt Foundation. Some rights reserved.
- **
- ** This file is part of the QxtCore module of the Qxt library.
- **
- ** This library is free software; you can redistribute it and/or modify it
- ** under the terms of the Common Public License, version 1.0, as published
- ** by IBM, and/or under the terms of the GNU Lesser General Public License,
- ** version 2.1, as published by the Free Software Foundation.
- **
- ** This file is provided "AS IS", without WARRANTIES OR CONDITIONS OF ANY
- ** KIND, EITHER EXPRESS OR IMPLIED INCLUDING, WITHOUT LIMITATION, ANY
- ** WARRANTIES OR CONDITIONS OF TITLE, NON-INFRINGEMENT, MERCHANTABILITY OR
- ** FITNESS FOR A PARTICULAR PURPOSE.
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- ** You should have received a copy of the CPL and the LGPL along with this
- ** file. See the LICENSE file and the cpl1.0.txt/lgpl-2.1.txt files
- ** included with the source distribution for more information.
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- ****************************************************************************/
- /*!
- \class QxtNullable QxtNullable
- \inmodule QxtCore
- \brief distinct null value compatible with any data type.
- in general it's a templated abstraction to allow any data type to be
- expressed with a null value distinct from any real value. An example
- of such a use is for optional arguments.
- \n
- prepare a function for argument skipping:
- \code
- void somefunction( qxtNull(int,a) , qxtNull(int,b) )
- {
- if (!a.isNull())
- {
- int i = a.value();
- //do something with i
- }
- if (!b.isNull())
- {
- int x = b.value();
- //do something with x
- }
- }
- \endcode
- usage:
- \code
- somefunction(SKIP,1,2);
- somefunction(3,4);
- somefunction(3,SKIP,6);
- somefunction(1);
- \endcode
- */
- #ifndef QXTNULLABLE_H
- #define QXTNULLABLE_H
- #include <qxtglobal.h>
- /*! \relates QxtNullable
- * defines a skipable argument with type \a t and variable name \a n
- */
- #define qxtNull(t,n) QxtNullable<t> n = QxtNullable<t>()
- #include <qxtnull.h>
- template<typename T>
- class /*QXT_CORE_EXPORT*/ QxtNullable
- {
- public:
- QxtNullable(QxtNull);
- QxtNullable(const T& p);
- QxtNullable();
- ///determinates if the Value is set to something meaningfull
- bool isNull() const;
- ///delete Value
- void nullify();
- T& value() const;
- operator T() const;
- void operator=(const T& p);
- private:
- T* val;
- };
- template<typename T>
- QxtNullable<T>::QxtNullable(QxtNull)
- {
- val = 0;
- }
- template<typename T>
- QxtNullable<T>::QxtNullable(const T& p)
- {
- val = const_cast<T*>(&p);
- }
- template<typename T>
- QxtNullable<T>::QxtNullable()
- {
- val = 0;
- }
- template<typename T>
- QxtNullable<T>::operator T() const
- {
- return *val;
- }
- template<typename T>
- T& QxtNullable<T>::value() const
- {
- return *val;
- }
- template<typename T>
- bool QxtNullable<T>::isNull() const
- {
- return (val == 0);
- }
- template<typename T>
- void QxtNullable<T>::nullify()
- {
- val = 0;
- }
- template<typename T>
- void QxtNullable<T>::operator=(const T & p)
- {
- val = const_cast<T*>(&p);
- }
- #endif