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 strict 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\_DEFINE\_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.Append(element);      // ok
  55     list.Append(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. The use of the latter is especially discouraged as
  70 it is not only unsafe but is also much less efficient than
  71 \helpref{wxArrayString}{wxarraystring} class.
  72
  73 In the documentation of the list classes below, you should replace wxNode with
  74 wxListName::Node and wxObject with the list element type (i.e. the first
  75 parameter of WX\_DECLARE\_LIST) for the template lists.
  76
  77 \wxheading{Derived from}
  78
  79 \helpref{wxObject}{wxobject}
  80
  81 \wxheading{Include files}
  82
  83 <wx/list.h>
  84
  85 \wxheading{Example}
  86
  87 It is very common to iterate on a list as follows:
  88
  89 \begin{verbatim}
  90   ...
  91   wxWindow *win1 = new wxWindow(...);
  92   wxWindow *win2 = new wxWindow(...);
  93
  94   wxList SomeList;
  95   SomeList.Append(win1);
  96   SomeList.Append(win2);
  97
  98   ...
  99
 100   wxNode *node = SomeList.GetFirst();
 101   while (node)
 102   {
 103     wxWindow *win = node->GetData();
 104     ...
 105     node = node->GetNext();
 106   }
 107 \end{verbatim}
 108
 109 To delete nodes in a list as the list is being traversed, replace
 110
 111 \begin{verbatim}
 112     ...
 113     node = node->GetNext();
 114     ...
 115 \end{verbatim}
 116
 117 with
 118
 119 \begin{verbatim}
 120     ...
 121     delete win;
 122     delete node;
 123     node = SomeList.GetFirst();
 124     ...
 125 \end{verbatim}
 126
 127 See \helpref{wxNode}{wxnode} for members that retrieve the data associated with a node, and
 128 members for getting to the next or previous node.
 129
 130 \wxheading{See also}
 131
 132 \helpref{wxNode}{wxnode}, \helpref{wxStringList}{wxstringlist},
 133 \helpref{wxArray}{wxarray}
 134
 135 \latexignore{\rtfignore{\wxheading{Members}}}
 136
 137 \membersection{wxList::wxList}
 138
 139 \func{}{wxList}{\void}
 140
 141 \func{}{wxList}{\param{unsigned int}{ key\_type}}
 142
 143 \func{}{wxList}{\param{int}{ n}, \param{wxObject *}{objects[]}}
 144
 145 \func{}{wxList}{\param{wxObject *}{object}, ...}
 146
 147 Constructors. {\it key\_type} is one of wxKEY\_NONE, wxKEY\_INTEGER, or wxKEY\_STRING,
 148 and indicates what sort of keying is required (if any).
 149
 150 {\it objects} is an array of {\it n} objects with which to initialize the list.
 151
 152 The variable-length argument list constructor must be supplied with a
 153 terminating NULL.
 154
 155 \membersection{wxList::\destruct{wxList}}
 156
 157 \func{}{\destruct{wxList}}{\void}
 158
 159 Destroys the list.  Also destroys any remaining nodes, but does not destroy
 160 client data held in the nodes.
 161
 162 \membersection{wxList::Append}\label{wxlistappend}
 163
 164 \func{wxNode *}{Append}{\param{wxObject *}{object}}
 165
 166 \func{wxNode *}{Append}{\param{long}{ key}, \param{wxObject *}{object}}
 167
 168 \func{wxNode *}{Append}{\param{const wxString\& }{key}, \param{wxObject *}{object}}
 169
 170 Appends a new {\bf wxNode} to the end of the list and puts a pointer to the
 171 \rtfsp{\it object} in the node.  The last two forms store a key with the object for
 172 later retrieval using the key. The new node is returned in each case.
 173
 174 The key string is copied and stored by the list implementation.
 175
 176 \membersection{wxList::Clear}\label{wxlistclear}
 177
 178 \func{void}{Clear}{\void}
 179
 180 Clears the list (but does not delete the client data stored with each node
 181 unless you called DeleteContents(TRUE), in which case it deletes data).
 182
 183 \membersection{wxList::DeleteContents}\label{wxlistdeletecontents}
 184
 185 \func{void}{DeleteContents}{\param{bool}{ destroy}}
 186
 187 If {\it destroy} is TRUE, instructs the list to call {\it delete} on the client contents of
 188 a node whenever the node is destroyed. The default is FALSE.
 189
 190 \membersection{wxList::DeleteNode}\label{wxlistdeletenode}
 191
 192 \func{bool}{DeleteNode}{\param{wxNode *}{node}}
 193
 194 Deletes the given node from the list, returning TRUE if successful.
 195
 196 \membersection{wxList::DeleteObject}\label{wxlistdeleteobject}
 197
 198 \func{bool}{DeleteObject}{\param{wxObject *}{object}}
 199
 200 Finds the given client {\it object} and deletes the appropriate node from the list, returning
 201 TRUE if successful. The application must delete the actual object separately.
 202
 203 \membersection{wxList::Find}\label{wxlistfind}
 204
 205 \func{wxNode *}{Find}{\param{long}{ key}}
 206
 207 \func{wxNode *}{Find}{\param{const wxString\& }{key}}
 208
 209 Returns the node whose stored key matches {\it key}. Use on a keyed list only.
 210
 211 \membersection{wxList::GetCount}\label{wxlistgetcount}
 212
 213 \constfunc{size\_t}{GetCount}{\void}
 214
 215 Returns the number of elements in the list.
 216
 217 \membersection{wxList::GetFirst}\label{wxlistgetfirst}
 218
 219 \func{wxNode *}{GetFirst}{\void}
 220
 221 Returns the first node in the list (NULL if the list is empty).
 222
 223 \membersection{wxList::GetLast}\label{wxlistgetlast}
 224
 225 \func{wxNode *}{GetLast}{\void}
 226
 227 Returns the last node in the list (NULL if the list is empty).
 228
 229 \membersection{wxList::IndexOf}\label{wxlistindexof}
 230
 231 \func{int}{IndexOf}{\param{wxObject*}{ obj }}
 232
 233 Returns the index of {\it obj} within the list or NOT\_FOUND if {\it obj}
 234 is not found in the list.
 235
 236 \membersection{wxList::Insert}\label{wxlistinsert}
 237
 238 \func{wxNode *}{Insert}{\param{wxObject *}{object}}
 239
 240 Insert object at front of list.
 241
 242 \func{wxNode *}{Insert}{\param{size\_t }{position}, \param{wxObject *}{object}}
 243
 244 Insert object before {\it position}, i.e. the index of the new item in the
 245 list will be equal to {\it position}. {\it position} should be less than or
 246 equal to \helpref{GetCount}{wxlistgetcount}; if it is equal to it, this is the
 247 same as calling \helpref{Append}{wxlistappend}.
 248
 249 \func{wxNode *}{Insert}{\param{wxNode *}{node}, \param{wxObject *}{object}}
 250
 251 Inserts the object before the given {\it node}.
 252
 253 \membersection{wxList::Item}\label{wxlistitem}
 254
 255 \constfunc{wxNode *}{Item}{\param{size\_t }{index}}
 256
 257 Returns the node at given position in the list.
 258
 259 \membersection{wxList::Member}\label{wxlistmember}
 260
 261 \func{wxNode *}{Member}{\param{wxObject *}{object}}
 262
 263 {\bf NB:} This function is deprecated, use \helpref{Find}{wxlistfind} instead.
 264
 265 Returns the node associated with {\it object} if it is in the list, NULL otherwise.
 266
 267 \membersection{wxList::Nth}\label{wxlistnth}
 268
 269 \func{wxNode *}{Nth}{\param{int}{ n}}
 270
 271 {\bf NB:} This function is deprecated, use \helpref{Item}{wxlistitem} instead.
 272
 273 Returns the {\it nth} node in the list, indexing from zero (NULL if the list is empty
 274 or the nth node could not be found).
 275
 276 \membersection{wxList::Number}\label{wxlistnumber}
 277
 278 \func{int}{Number}{\void}
 279
 280 {\bf NB:} This function is deprecated, use \helpref{GetCount}{wxlistgetcount} instead.
 281
 282 Returns the number of elements in the list.
 283
 284 \membersection{wxList::Sort}\label{wxlistsort}
 285
 286 \func{void}{Sort}{\param{wxSortCompareFunction}{ compfunc}}
 287
 288 \begin{verbatim}
 289   // Type of compare function for list sort operation (as in 'qsort')
 290   typedef int (*wxSortCompareFunction)(const void *elem1, const void *elem2);
 291 \end{verbatim}
 292
 293 Allows the sorting of arbitrary lists by giving
 294 a function to compare two list elements. We use the system {\bf qsort} function
 295 for the actual sorting process.
 296
 297 If you use untyped wxList the sort function receives pointers to wxObject
 298 pointers (wxObject **), so be careful to dereference appropriately - but,
 299 of course, a better solution is to use list of appropriate type defined with
 300 {\tt WX\_DECLARE\_LIST}.
 301
 302 Example:
 303
 304 \begin{verbatim}
 305   int listcompare(const void *arg1, const void *arg2)
 306   {
 307     return(compare(**(wxString **)arg1,    // use the wxString 'compare'
 308                    **(wxString **)arg2));  // function
 309   }
 310
 311   void main()
 312   {
 313     wxList list;
 314
 315     list.Append(new wxString("DEF"));
 316     list.Append(new wxString("GHI"));
 317     list.Append(new wxString("ABC"));
 318     list.Sort(listcompare);
 319   }
 320 \end{verbatim}
 321