shared source/vb/language/shared/tristate.h

   1 //-------------------------------------------------------------------------------------------------
   2 //
   3 //  Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 //-------------------------------------------------------------------------------------------------
   6
   7 #pragma once
   8
   9 template <class T>
  10 class TriState
  11 {
  12 public:
  13     TriState() :
  14       m_hasValue(false)
  15     {
  16     }
  17
  18     TriState(T value) :
  19         m_hasValue(true),
  20         m_value(value)
  21     {
  22     }
  23
  24     ~TriState()
  25     {
  26     }
  27
  28     bool HasValue() const
  29     {
  30          return m_hasValue;
  31     }
  32
  33     const T& GetValue() const
  34     {
  35         ThrowIfFalse(HasValue());
  36         return m_value;
  37     }
  38
  39     T& GetValue()
  40     {
  41         ThrowIfFalse(HasValue());
  42         return m_value;
  43     }
  44
  45     T GetValueOrDefault( _In_ const T& defaultValue) const
  46     {
  47         if ( !HasValue() )
  48         {
  49             return defaultValue;
  50         }
  51         return m_value;
  52     }
  53
  54     void SetValue(T value)
  55     {
  56         m_value = value;
  57         m_hasValue = true;
  58     }
  59
  60     void ClearValue()
  61     {
  62         ClearValue(T());
  63     }
  64
  65     void ClearValue(const T& defaultValue)
  66     {
  67         m_hasValue = false;
  68         m_value = defaultValue;
  69     }
  70
  71 private:
  72     bool m_hasValue;
  73     T m_value;
  74 };