text: /****************************************************************************
   * Copyright (C) from 2009 to Present EPAM Systems.
   *
   * This file is part of Indigo toolkit.
   *
   * 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 __nullable__
  #define __nullable__
  
  #include "base_cpp/array.h"
  #include "base_cpp/exception.h"
  
  namespace indigo
  {
  
      DECL_EXCEPTION(NullableError);
  
      template <typename T>
      class Nullable
      {
      public:
          Nullable() : _has_value(false)
          {
              variable_name.readString("<Undefined>", true);
          }
  
          const T& get() const
          {
              if (!_has_value)
                  throw Error("\"%s\" variable was not set", variable_name.ptr());
              return _value;
          }
  
          operator const T&() const
          {
              return get();
          }
  
          Nullable<T>& operator=(const T& value)
          {
              set(value);
              return *this;
          }
  
          void set(const T& value)
          {
              _value = value;
              _has_value = true;
          }
  
          void reset()
          {
              _has_value = false;
          }
  
          bool hasValue() const
          {
              return _has_value;
          }
  
          void setName(const char* name)
          {
              variable_name.readString(name, true);
          }
  
          DECL_TPL_ERROR(NullableError);
  
      private:
          T _value;
          bool _has_value;
          Array<char> variable_name;
      };
  
  } // namespace indigo
  
  #endif // __nullable__
  