docs/latex/wx/objectdataptr.tex

   1 \section{\class{wxObjectDataPtr<T>}}\label{wxobjectdataptr}
   2
   3 This is helper template class primarily written to avoid memory
   4 leaks because of missing calls to \helpref{wxObjectRefData::DecRef}{wxobjectrefdatadecref}.
   5
   6 Despite the name this template can actually be used as a
   7 smart pointer for any class implementing the reference
   8 counting interface which only consists of the two methods
   9 {\bf T::IncRef()} and {\bf T::DecRef()}.
  10
  11 The difference to \helpref{wxSharedPtr}{wxsharedptr} is that
  12 wxObjectDataPtr relies on the reference counting to be in
  13 the class pointed to where as wxSharedPtr implements the
  14 reference counting itself.
  15
  16 \wxheading{See also}
  17
  18 \helpref{wxObject}{wxobject},
  19 \helpref{wxObjectRefData}{wxobjectrefdata},
  20 \helpref{Reference counting}{trefcount}
  21
  22 \helpref{wxSharedPtr}{wxsharedptr},
  23 \helpref{wxScopedPtr}{wxscopedptrtemplate},
  24 \helpref{wxWeakRef}{wxweakref}
  25
  26
  27 \wxheading{Derived from}
  28
  29 No base class
  30
  31 \wxheading{Include files}
  32
  33 <object.h>
  34
  35 \wxheading{Data structures}
  36
  37 {\small%
  38 \begin{verbatim}
  39 typedef T element_type
  40 \end{verbatim}
  41 }%
  42
  43 \wxheading{Example}
  44
  45 \begin{verbatim}
  46
  47 class MyCarRefData: public wxObjectRefData
  48 {
  49 public:
  50     MyCarRefData()  { m_price = 0; }
  51
  52     MyCarRefData( const MyCarRefData& data )
  53         : wxObjectRefData()
  54     {
  55         m_price = data.m_price;
  56     }
  57
  58     void SetPrice( int price )  { m_price = price; }
  59     int GetPrice()              { return m_price; }
  60
  61 protected:
  62     int m_price;
  63 };
  64
  65 class MyCar
  66 {
  67 public:
  68     MyCar( int price ) : m_data( new MyCarRefData )
  69     {
  70         m_data->SetPrice( price );
  71     }
  72
  73     MyCar& operator =( const MyCar& tocopy )
  74     {
  75         m_data = tocopy.m_data;
  76         return *this;
  77     }
  78
  79     bool operator == ( const MyCar& other ) const
  80     {
  81         if (m_data.get() == other.m_data.get()) return true;
  82         return (m_data->GetPrice() == other.m_data->GetPrice());
  83     }
  84
  85     void SetPrice( int price )
  86     {
  87        UnShare();
  88        m_data->SetPrice( price );
  89     }
  90
  91     int GetPrice() const
  92     {
  93        return m_data->GetPrice();
  94     }
  95
  96     wxObjectDataPtr<MyCarRefData> m_data;
  97
  98 protected:
  99     void UnShare()
 100     {
 101         if (m_data->GetRefCount() == 1)
 102             return;
 103
 104         m_data.reset( new MyCarRefData( *m_data ) );
 105     }
 106 };
 107
 108 \end{verbatim}
 109
 110
 111 \latexignore{\rtfignore{\wxheading{Members}}}
 112
 113 \membersection{wxObjectDataPtr<T>::wxObjectDataPtr<T>}\label{wxobjectdataptrwxobjectdataptr}
 114
 115 \func{wxEXPLICIT}{wxObjectDataPtr<T>}{\param{T* }{ptr = NULL}}
 116
 117 Constructor. {\it ptr} is a pointer to the reference
 118 counted object to which this class points. If {\it ptr}
 119 is not NULL {\bf T::IncRef()} will be called on the
 120 object.
 121
 122 \func{}{wxObjectDataPtr<T>}{\param{const wxObjectDataPtr<T>\& }{tocopy}}
 123
 124 This copy constructor increases the count of the reference
 125 counted object to which {\it tocopy} points and then this
 126 class will point to, as well.
 127
 128 \membersection{wxObjectDataPtr<T>::\destruct{wxObjectDataPtr<T>}}\label{wxobjectdataptrdtor}
 129
 130 \func{}{\destruct{wxObjectDataPtr<T>}}{\void}
 131
 132 Decreases the reference count of the object to which this
 133 class points.
 134
 135 \membersection{wxObjectDataPtr<T>::operator unspecified\_bool\_type}\label{wxobjectdataptroperatorbool}
 136
 137 \constfunc{}{operator unspecified\_bool\_type}{\void}
 138
 139 Conversion to a boolean expression (in a variant which is not
 140 convertable to anything but a boolean expression). If this class
 141 contains a valid pointer it will return {\it true}, if it contains
 142 a NULL pointer it will return {\it false}.
 143
 144 \membersection{wxObjectDataPtr<T>::operator*}\label{wxobjectdataptroperatorreft}
 145
 146 \constfunc{T \&}{operator*}{\void}
 147
 148 Returns a reference to the object. If the internal pointer is NULL
 149 this method will cause an assert in debug mode.
 150
 151 \membersection{wxObjectDataPtr<T>::operator->}\label{wxobjectdataptroperatorpointer}
 152
 153 \constfunc{T*}{operator->}{\void}
 154
 155 Returns a pointer to the reference counted object to which
 156 this class points. If this the internal pointer is NULL,
 157 this method will assert in debug mode.
 158
 159 \membersection{wxObjectDataPtr<T>::operator=}\label{wxobjectdataptroperatorassign}
 160
 161 \func{wxObjectDataPtr<T>\& operator}{operator=}{\param{const wxObjectDataPtr<T>\& }{tocopy}}
 162
 163 \func{wxObjectDataPtr<T>\& operator}{operator=}{\param{T* }{ptr}}
 164
 165 Assignment operators.
 166
 167 \membersection{wxObjectDataPtr<T>::get}\label{wxobjectdataptrget}
 168
 169 \constfunc{T*}{get}{\void}
 170
 171 Gets a pointer to the reference counted object to which
 172 this class points.
 173
 174 \membersection{wxObjectDataPtr<T>::reset}\label{wxobjectdataptrreset}
 175
 176 \func{void}{reset}{\param{T* }{ptr}}
 177
 178 Reset this class to {\it ptr} which points to a reference
 179 counted object and calls {\bf T::DecRef()} on the previously
 180 owned object.