docs/latex/wx/list.tex

   1 \section{\class{wxList}}\label{wxlist}
   2
   3 wxList classes provide linked list functionality for wxWindows, and for an
   4 application if it wishes.  Depending on the form of constructor used, a list
   5 can be keyed on integer or string keys to provide a primitive look-up ability.
   6 See \helpref{wxHashTable}{wxhashtable}\rtfsp for a faster method of storage
   7 when random access is required.
   8
   9 While wxList class in the previous versions of wxWindows only could contain
  10 elements of type wxObject and had essentially untyped interface (thus allowing
  11 you to put apples in the list and read back oranges from it), the new wxList
  12 classes family may contain elements of any type and has much more stricter type
  13 checking. Unfortunately, it also requires an additional line to be inserted in
  14 your program for each list class you use (which is the only solution short of
  15 using templates which is not done in wxWindows because of portability issues).
  16
  17 The general idea is to have the base class wxListBase working with {\it void *}
  18 data but make all of its dangerous (because untyped) functions protected, so
  19 that they can only be used from derived classes which, in turn, expose a type
  20 safe interface. With this approach a new wxList-like class must be defined for
  21 each list type (i.e. list of ints, of wxStrings or of MyObjects). This is done
  22 with {\it WX\_DECLARE\_LIST} and {\it WX\_IMPLEMENT\_LIST} macros like this
  23 (notice the similarity with WX\_DECLARE\_OBJARRAY and WX\_IMPLEMENT\_OBJARRAY
  24 macros):
  25
  26 \wxheading{Example}
  27
  28 {\small%
  29 \begin{verbatim}
  30     // this part might be in a header or source (.cpp) file
  31     class MyListElement
  32     {
  33         ... // whatever
  34     };
  35
  36     // declare our list class: this macro declares and partly implements MyList
  37     // class (which derives from wxListBase)
  38     WX_DECLARE_LIST(MyListElement, MyList)
  39
  40     ...
  41
  42     // the only requirment for the rest is to be AFTER the full declaration of
  43     // MyListElement (for WX_DECLARE_LIST forward declaration is enough), but
  44     // usually it will be found in the source file and not in the header
  45
  46     #include <wx/listimpl.cpp>
  47     WX_DEFINE_LIST(MyList)
  48
  49     // now MyList class may be used as a usual wxList, but all of its methods
  50     // will take/return the objects of the right (i.e. MyListElement) type. You
  51     // also have MyList::Node type which is the type-safe version of wxNode.
  52     MyList list;
  53     MyListElement element;
  54     list.Add(element);      // ok
  55     list.Add(17);           // error: incorrect type
  56
  57     // let's iterate over the list
  58     for ( MyList::Node *node = list.GetFirst(); node; node = node->GetNext() )
  59     {
  60         MyListElement *current = node->GetData();
  61
  62         ...process the current element...
  63     }
  64 \end{verbatim}
  65 }
  66
  67 For compatibility with previous versions wxList and wxStringList classes are
  68 still defined, but their usage is deprecated and they will disappear in the
  69 future versions completely.
  70
  71 \wxheading{Derived from}
  72
  73 \helpref{wxObject}{wxobject}
  74
  75 {\bf WARNING: } the rest of documentation may be out-of-date.
  76
  77 \wxheading{Example}
  78
  79 It is very common to iterate on a list as follows:
  80
  81 \begin{verbatim}
  82   ...
  83   wxPoint *point1 = new wxPoint(100, 100);
  84   wxPoint *point2 = new wxPoint(200, 200);
  85
  86   wxList SomeList;
  87   SomeList.Append(point1);
  88   SomeList.Append(point2);
  89
  90   ...
  91
  92   wxNode *node = SomeList.First();
  93   while (node)
  94   {
  95     wxPoint *point = (wxPoint *)node->Data();
  96     ...
  97     node = node->Next();
  98   }
  99 \end{verbatim}
 100
 101 To delete nodes in a list as the list is being traversed, replace
 102
 103 \begin{verbatim}
 104     ...
 105     node = node->Next();
 106     ...
 107 \end{verbatim}
 108
 109 with
 110
 111 \begin{verbatim}
 112     ...
 113     delete point;
 114     delete node;
 115     node = SomeList.First();
 116     ...
 117 \end{verbatim}
 118
 119 See \helpref{wxNode}{wxnode} for members that retrieve the data associated with a node, and
 120 members for getting to the next or previous node.
 121
 122 Note that a cast is required when retrieving the data from a node.  Although a
 123 node is defined to store objects of type {\bf wxObject} and derived types, other
 124 types (such as char*) may be used with appropriate casting.
 125
 126 \wxheading{See also}
 127
 128 \helpref{wxNode}{wxnode}, \helpref{wxStringList}{wxstringlist},
 129 \helpref{wxArray}{wxarray}
 130
 131 \latexignore{\rtfignore{\wxheading{Members}}}
 132
 133 \membersection{wxList::wxList}
 134
 135 \func{}{wxList}{\void}
 136
 137 \func{}{wxList}{\param{unsigned int}{ key\_type}}
 138
 139 \func{}{wxList}{\param{int}{ n}, \param{wxObject *}{objects[]}}
 140
 141 \func{}{wxList}{\param{wxObject *}{object}, ...}
 142
 143 Constructors. {\it key\_type} is one of wxKEY\_NONE, wxKEY\_INTEGER, or wxKEY\_STRING,
 144 and indicates what sort of keying is required (if any).
 145
 146 {\it objects} is an array of {\it n} objects with which to initialize the list.
 147
 148 The variable-length argument list constructor must be supplied with a
 149 terminating NULL.
 150
 151 \membersection{wxList::\destruct{wxList}}
 152
 153 \func{}{\destruct{wxList}}{\void}
 154
 155 Destroys the list.  Also destroys any remaining nodes, but does not destroy
 156 client data held in the nodes.
 157
 158 \membersection{wxList::Append}
 159
 160 \func{wxNode *}{Append}{\param{wxObject *}{object}}
 161
 162 \func{wxNode *}{Append}{\param{long}{ key}, \param{wxObject *}{object}}
 163
 164 \func{wxNode *}{Append}{\param{const wxString\& }{key}, \param{wxObject *}{object}}
 165
 166 Appends a new {\bf wxNode} to the end of the list and puts a pointer to the
 167 \rtfsp{\it object} in the node.  The last two forms store a key with the object for
 168 later retrieval using the key. The new node is returned in each case.
 169
 170 The key string is copied and stored by the list implementation.
 171
 172 \membersection{wxList::Clear}
 173
 174 \func{void}{Clear}{\void}
 175
 176 Clears the list (but does not delete the client data stored with each node).
 177
 178 \membersection{wxList::DeleteContents}
 179
 180 \func{void}{DeleteContents}{\param{bool}{ destroy}}
 181
 182 If {\it destroy} is TRUE, instructs the list to call {\it delete} on the client contents of
 183 a node whenever the node is destroyed. The default is FALSE.
 184
 185 \membersection{wxList::DeleteNode}
 186
 187 \func{bool}{DeleteNode}{\param{wxNode *}{node}}
 188
 189 Deletes the given node from the list, returning TRUE if successful.
 190
 191 \membersection{wxList::DeleteObject}
 192
 193 \func{bool}{DeleteObject}{\param{wxObject *}{object}}
 194
 195 Finds the given client {\it object} and deletes the appropriate node from the list, returning
 196 TRUE if successful. The application must delete the actual object separately.
 197
 198 \membersection{wxList::Find}
 199
 200 \func{wxNode *}{Find}{\param{long}{ key}}
 201
 202 \func{wxNode *}{Find}{\param{const wxString\& }{key}}
 203
 204 Returns the node whose stored key matches {\it key}. Use on a keyed list only.
 205
 206 \membersection{wxList::First}
 207
 208 \func{wxNode *}{First}{\void}
 209
 210 Returns the first node in the list (NULL if the list is empty).
 211
 212 \membersection{wxList::IndexOf}
 213
 214 \func{int}{IndexOf}{\param{wxObject*}{ obj }}
 215
 216 Returns the index of {\it obj} within the list or NOT\_FOUND if {\it obj}
 217 is not found in the list.
 218
 219 \membersection{wxList::Insert}
 220
 221 \func{wxNode *}{Insert}{\param{wxObject *}{object}}
 222
 223 Insert object at front of list.
 224
 225 \func{wxNode *}{Insert}{\param{wxNode *}{position}, \param{wxObject *}{object}}
 226
 227 Insert object before {\it position}.
 228
 229
 230 \membersection{wxList::Last}
 231
 232 \func{wxNode *}{Last}{\void}
 233
 234 Returns the last node in the list (NULL if the list is empty).
 235
 236 \membersection{wxList::Member}
 237
 238 \func{wxNode *}{Member}{\param{wxObject *}{object}}
 239
 240 Returns the node associated with {\it object} if it is in the list, NULL otherwise.
 241
 242 \membersection{wxList::Nth}
 243
 244 \func{wxNode *}{Nth}{\param{int}{ n}}
 245
 246 Returns the {\it nth} node in the list, indexing from zero (NULL if the list is empty
 247 or the nth node could not be found).
 248
 249 \membersection{wxList::Number}
 250
 251 \func{int}{Number}{\void}
 252
 253 Returns the number of elements in the list.
 254
 255 \membersection{wxList::Sort}
 256
 257 \func{void}{Sort}{\param{wxSortCompareFunction}{ compfunc}}
 258
 259 \begin{verbatim}
 260   // Type of compare function for list sort operation (as in 'qsort')
 261   typedef int (*wxSortCompareFunction)(const void *elem1, const void *elem2);
 262 \end{verbatim}
 263
 264 Allows the sorting of arbitrary lists by giving
 265 a function to compare two list elements. We use the system {\bf qsort} function
 266 for the actual sorting process. The sort function receives pointers to wxObject pointers (wxObject **),
 267 so be careful to dereference appropriately.
 268
 269 Example:
 270
 271 \begin{verbatim}
 272   int listcompare(const void *arg1, const void *arg2)
 273   {
 274     return(compare(**(wxString **)arg1,    // use the wxString 'compare'
 275                    **(wxString **)arg2));  // function
 276   }
 277
 278   void main()
 279   {
 280     wxList list;
 281
 282     list.Append(new wxString("DEF"));
 283     list.Append(new wxString("GHI"));
 284     list.Append(new wxString("ABC"));
 285     list.Sort(listcompare);
 286   }
 287 \end{verbatim}
 288
 289