docs/latex/wx/scpdptr.tex

   1 \section{\class{wxScopedPtr}}\label{wxscopedptr}
   2
   3 This is a simple scoped smart pointer implementation that is similar to
   4 the \urlref{Boost}{http://www.boost.org/} smart pointers but rewritten to
   5 use macros instead.
   6
   7 A smart pointer holds a pointer to an object. The memory used by the object is
   8 deleted when the smart pointer goes out of scope. This class is different from
   9 the \texttt{std::auto\_ptr<>} in so far as it doesn't provide copy constructor
  10 nor assignment operator. This limits what you can do with it but is much less
  11 surprizing than the ``destructive copy'' behaviour of the standard class.
  12
  13 \wxheading{Example}
  14
  15 Below is an example of using a wxWindows scoped smart pointer and
  16 pointer array.
  17
  18 \begin{verbatim}
  19   class MyClass { /* ... */ };
  20
  21   // declare a smart pointer to a MyClass called wxMyClassPtr
  22   wxDECLARE_SCOPED_PTR(MyClass, wxMyClassPtr)
  23   // declare a smart pointer to an array of chars
  24   wxDECLARE_SCOPED_ARRAY(char, wxCharArray)
  25
  26   ...
  27
  28   // define the first pointer class, must be complete
  29   wxDEFINE_SCOPED_PTR(MyClass, wxMyClassPtr)
  30   // define the second pointer class
  31   wxDEFINE_SCOPED_ARRAY(char, wxCharArray)
  32
  33   // create an object with a new pointer to MyClass
  34   wxMyClassPtr theObj(new MyClass());
  35   // reset the pointer (deletes the previous one)
  36   theObj.reset(new MyClass());
  37
  38   // access the pointer
  39   theObj->MyFunc();
  40
  41   // create an object with a new array of chars
  42   wxCharArray theCharObj(new char[100]);
  43
  44   // access the array
  45   theCharObj[0] = "!";
  46 \end{verbatim}
  47
  48 \wxheading{Declaring new smart pointer types}
  49
  50 To declare the smart pointer class \texttt{CLASSNAME} containing pointes to a
  51 (possibly incomplete) type \texttt{TYPE} you should use
  52 \begin{verbatim}
  53     wxDECLARE_SCOPED_PTR( TYPE,     // type of the values
  54                                 CLASSNAME ); // name of the class
  55 \end{verbatim}
  56
  57 And later, when \texttt{TYPE} is fully defined, you must also use
  58 \begin{verbatim}
  59     wxDEFINE_SCOPED_PTR( TYPE, CLASSNAME );
  60 \end{verbatim}
  61 to implement the scoped pointer class.
  62
  63 The first argument of these macro is the pointer type, the second is the name
  64 of the new smart pointer class being created.  Below we will use wxScopedPtr to
  65 represent the scoped pointer class, but the user may create the class with any
  66 legal name.
  67
  68 Alternatively, if you don't have to separate the point of declaration and
  69 definition of this class and if you accept the standard naming convention, that
  70 is that the scoped pointer for the class \texttt{Foo} is called
  71 \texttt{FooPtr}, you can use a single macro which replaces two macros above:
  72 \begin{verbatim}
  73     wxDEFINE_SCOPED_PTR_TYPE( TYPE );
  74 \end{verbatim}
  75 Once again, in this cass \texttt{CLASSNAME} will be \texttt{TYPEPtr}.
  76
  77 \wxheading{Include files}
  78
  79 <wx/ptr\_scpd.h>
  80
  81 \wxheading{See also}
  82
  83 \helpref{wxScopedArray}{wxscopedarray}\rtfsp
  84
  85 \latexignore{\rtfignore{\wxheading{Members}}}
  86
  87 \membersection{wxScopedPtr::wxScopedPtr}
  88
  89 \func{}{explicit wxScopedPtr}{\param{type}{ * T = NULL}}
  90
  91 Creates the smart pointer with the given pointer or none if {\tt NULL}.  On
  92 compilers that support it, this uses the explicit keyword.
  93
  94
  95 \membersection{wxScopedPtr::\destruct{wxScopedPtr}}
  96
  97 \func{}{\destruct{wxScopedPtr}}{\void}
  98
  99 Destructor frees the pointer help by this object if it is not {\tt NULL}.
 100
 101
 102 \membersection{wxScopedPtr::release}
 103
 104 \func{T *}{release}{\void}
 105
 106 Returns the currently hold pointer and resets the smart pointer object to
 107 {\tt NULL}. After a call to this function the caller is responsible for
 108 deleting the pointer.
 109
 110
 111 \membersection{wxScopedPtr::reset}
 112
 113 \func{\void}{reset}{\param{T}{ p * = NULL}}
 114
 115 Deletes the currently held pointer and sets it to {\it p} or to NULL if no
 116 arguments are specified. This function does check to make sure that the
 117 pointer you are assigning is not the same pointer that is already stored.
 118
 119
 120 \membersection{wxScopedPtr::operator *}
 121
 122 \func{const T\&}{operator *}{\void}
 123
 124 This operator works like the standard C++ pointer operator to return the object
 125 being pointed to by the pointer.  If the pointer is NULL or invalid this will
 126 crash.
 127
 128
 129 \membersection{wxScopedPtr::operator -$>$} % TODO
 130
 131 \func{const T*}{operator -$>$}{\void} % TODO
 132
 133 This operator works like the standard C++ pointer operator to return the pointer
 134 in the smart pointer or NULL if it is empty.
 135
 136
 137 \membersection{wxScopedPtr::get}
 138
 139 \func{const T*}{get}{\void}
 140
 141 This operator gets the pointer stored in the smart pointer or returns NULL if
 142 there is none.
 143
 144
 145 \membersection{wxScopedPtr::swap}
 146
 147 \func{\void}{swap}{\param{wxScopedPtr}{ \& other}}
 148
 149 Swap the pointer inside the smart pointer with {\it other}. The pointer being
 150 swapped must be of the same type (hence the same class name).
 151
 152
 153
 154
 155 %%%%%%% wxScopedTiedPtr %%%%%%%
 156 \section{\class{wxScopedTiedPtr}}\label{wxscopedtiedptr}
 157
 158 This is a variation on the topic of \helpref{wxScopedPtr}{wxscopedptr}. This
 159 class is also a smart pointer but in addition it ``ties'' the pointer value to
 160 another variable. In other words, during the life time of this class the value
 161 of that variable is set to be the same as the value of the pointer itself and
 162 it is reset to its old value when the object is destroyed. This class is
 163 especially useful when converting the existing code (which may already store
 164 the pointers value in some variable) to the smart pointers.
 165
 166 \wxheading{Example}
 167
 168 \wxheading{Derives from}
 169
 170 \helpref{wxScopedPtr}{wxscopedptr}
 171
 172 \wxheading{Include files}
 173
 174 <wx/ptr\_scpd.h>
 175
 176 \latexignore{\rtfignore{\wxheading{Members}}}
 177
 178 \membersection{wxScopedTiedPtr::wxScopedTiedPtr}\label{wxscopedtiedptrctor}
 179
 180 \func{}{wxScopedTiedPtr}{\param{T **}{ppTie}, \param{T *}{ptr}}
 181
 182 Constructor creates a smart pointer initialized with \arg{ptr} and stores
 183 \arg{ptr} in the location specified by \arg{ppTie} which must not be
 184 {\tt NULL}.
 185
 186 \membersection{wxScopedTiedPtr::\destruct{wxScopedTiedPtr}}\label{wxscopedtiedptrdtor}
 187
 188 \func{}{\destruct{wxScopedTiedPtr}}{\void}
 189
 190 Destructor frees the pointer help by this object and restores the value stored
 191 at the tied location (as specified in the \helpref{constructor}{wxscopedtiedptrctor})
 192 to the old value.
 193
 194 Warning: this location may now contain an uninitialized value if it hadn't been
 195 initialized previously, in particular don't count on it magically being
 196 {\tt NULL}!
 197
 198