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 \wxheading{Include files}
  76
  77 <wx/list.h>
  78
  79 \wxheading{Example}
  80
  81 It is very common to iterate on a list as follows:
  82
  83 \begin{verbatim}
  84   ...
  85   wxWindow *win1 = new wxWindow(...);
  86   wxWindow *win2 = new wxWindow(...);
  87
  88   wxList SomeList;
  89   SomeList.Append(win1);
  90   SomeList.Append(win2);
  91
  92   ...
  93
  94   wxNode *node = SomeList.GetFirst();
  95   while (node)
  96   {
  97     wxWindow *win = (wxWindow *)node->Data();
  98     ...
  99     node = node->Next();
 100   }
 101 \end{verbatim}
 102
 103 To delete nodes in a list as the list is being traversed, replace
 104
 105 \begin{verbatim}
 106     ...
 107     node = node->Next();
 108     ...
 109 \end{verbatim}
 110
 111 with
 112
 113 \begin{verbatim}
 114     ...
 115     delete win;
 116     delete node;
 117     node = SomeList.GetFirst();
 118     ...
 119 \end{verbatim}
 120
 121 See \helpref{wxNode}{wxnode} for members that retrieve the data associated with a node, and
 122 members for getting to the next or previous node.
 123
 124 Note that a cast is required when retrieving the data from a node.  Although a
 125 node is defined to store objects of type {\bf wxObject} and derived types, other
 126 types (such as char*) may be used with appropriate casting.
 127
 128 \wxheading{See also}
 129
 130 \helpref{wxNode}{wxnode}, \helpref{wxStringList}{wxstringlist},
 131 \helpref{wxArray}{wxarray}
 132
 133 \latexignore{\rtfignore{\wxheading{Members}}}
 134
 135 \membersection{wxList::wxList}
 136
 137 \func{}{wxList}{\void}
 138
 139 \func{}{wxList}{\param{unsigned int}{ key\_type}}
 140
 141 \func{}{wxList}{\param{int}{ n}, \param{wxObject *}{objects[]}}
 142
 143 \func{}{wxList}{\param{wxObject *}{object}, ...}
 144
 145 Constructors. {\it key\_type} is one of wxKEY\_NONE, wxKEY\_INTEGER, or wxKEY\_STRING,
 146 and indicates what sort of keying is required (if any).
 147
 148 {\it objects} is an array of {\it n} objects with which to initialize the list.
 149
 150 The variable-length argument list constructor must be supplied with a
 151 terminating NULL.
 152
 153 \membersection{wxList::\destruct{wxList}}
 154
 155 \func{}{\destruct{wxList}}{\void}
 156
 157 Destroys the list.  Also destroys any remaining nodes, but does not destroy
 158 client data held in the nodes.
 159
 160 \membersection{wxList::Append}
 161
 162 \func{wxNode *}{Append}{\param{wxObject *}{object}}
 163
 164 \func{wxNode *}{Append}{\param{long}{ key}, \param{wxObject *}{object}}
 165
 166 \func{wxNode *}{Append}{\param{const wxString\& }{key}, \param{wxObject *}{object}}
 167
 168 Appends a new {\bf wxNode} to the end of the list and puts a pointer to the
 169 \rtfsp{\it object} in the node.  The last two forms store a key with the object for
 170 later retrieval using the key. The new node is returned in each case.
 171
 172 The key string is copied and stored by the list implementation.
 173
 174 \membersection{wxList::Clear}
 175
 176 \func{void}{Clear}{\void}
 177
 178 Clears the list (but does not delete the client data stored with each node).
 179
 180 \membersection{wxList::DeleteContents}\label{wxlistdeletecontents}
 181
 182 \func{void}{DeleteContents}{\param{bool}{ destroy}}
 183
 184 If {\it destroy} is TRUE, instructs the list to call {\it delete} on the client contents of
 185 a node whenever the node is destroyed. The default is FALSE.
 186
 187 \membersection{wxList::DeleteNode}
 188
 189 \func{bool}{DeleteNode}{\param{wxNode *}{node}}
 190
 191 Deletes the given node from the list, returning TRUE if successful.
 192
 193 \membersection{wxList::DeleteObject}
 194
 195 \func{bool}{DeleteObject}{\param{wxObject *}{object}}
 196
 197 Finds the given client {\it object} and deletes the appropriate node from the list, returning
 198 TRUE if successful. The application must delete the actual object separately.
 199
 200 \membersection{wxList::Find}
 201
 202 \func{wxNode *}{Find}{\param{long}{ key}}
 203
 204 \func{wxNode *}{Find}{\param{const wxString\& }{key}}
 205
 206 Returns the node whose stored key matches {\it key}. Use on a keyed list only.
 207
 208 \membersection{wxList::GetFirst}
 209
 210 \func{wxNode *}{GetFirst}{\void}
 211
 212 Returns the first node in the list (NULL if the list is empty).
 213
 214 \membersection{wxList::IndexOf}
 215
 216 \func{int}{IndexOf}{\param{wxObject*}{ obj }}
 217
 218 Returns the index of {\it obj} within the list or NOT\_FOUND if {\it obj}
 219 is not found in the list.
 220
 221 \membersection{wxList::Insert}
 222
 223 \func{wxNode *}{Insert}{\param{wxObject *}{object}}
 224
 225 Insert object at front of list.
 226
 227 \func{wxNode *}{Insert}{\param{wxNode *}{position}, \param{wxObject *}{object}}
 228
 229 Insert object before {\it position}.
 230
 231
 232 \membersection{wxList::GetLast}
 233
 234 \func{wxNode *}{GetLast}{\void}
 235
 236 Returns the last node in the list (NULL if the list is empty).
 237
 238 \membersection{wxList::Member}
 239
 240 \func{wxNode *}{Member}{\param{wxObject *}{object}}
 241
 242 Returns the node associated with {\it object} if it is in the list, NULL otherwise.
 243
 244 \membersection{wxList::Nth}
 245
 246 \func{wxNode *}{Nth}{\param{int}{ n}}
 247
 248 Returns the {\it nth} node in the list, indexing from zero (NULL if the list is empty
 249 or the nth node could not be found).
 250
 251 \membersection{wxList::Number}
 252
 253 \func{int}{Number}{\void}
 254
 255 Returns the number of elements in the list.
 256
 257 \membersection{wxList::Sort}
 258
 259 \func{void}{Sort}{\param{wxSortCompareFunction}{ compfunc}}
 260
 261 \begin{verbatim}
 262   // Type of compare function for list sort operation (as in 'qsort')
 263   typedef int (*wxSortCompareFunction)(const void *elem1, const void *elem2);
 264 \end{verbatim}
 265
 266 Allows the sorting of arbitrary lists by giving
 267 a function to compare two list elements. We use the system {\bf qsort} function
 268 for the actual sorting process. The sort function receives pointers to wxObject pointers (wxObject **),
 269 so be careful to dereference appropriately.
 270
 271 Example:
 272
 273 \begin{verbatim}
 274   int listcompare(const void *arg1, const void *arg2)
 275   {
 276     return(compare(**(wxString **)arg1,    // use the wxString 'compare'
 277                    **(wxString **)arg2));  // function
 278   }
 279
 280   void main()
 281   {
 282     wxList list;
 283
 284     list.Append(new wxString("DEF"));
 285     list.Append(new wxString("GHI"));
 286     list.Append(new wxString("ABC"));
 287     list.Sort(listcompare);
 288   }
 289 \end{verbatim}
 290
 291