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1 /////////////////////////////////////////////////////////////////////////////
2 // Name: container.h
3 // Purpose: topic overview
4 // Author: wxWidgets team
5 // RCS-ID: $Id$
6 // Licence: wxWindows licence
7 /////////////////////////////////////////////////////////////////////////////
8
9 /**
10
11 @page overview_container Container Classes
12
13 Classes: wxList<T>, wxArray<T>, wxVector<T>, wxStack<T>, wxHashMap, wxHashSet
14
15 @section overview_container_intro Overview
16
17 For historical reasons, wxWidgets uses custom container classes internally.
18 This was unfortunately unavoidable during a long time when the standard library
19 wasn't widely available and can't be easily changed even now that it is for
20 compatibility reasons. If you are building your own version of the library and
21 don't care about compatibility nor slight (less than 5%) size penalty imposed
22 by the use of STL classes, you may choose to use the "STL" build of wxWidgets
23 in which these custom classes are replaced with their standard counterparts and
24 only read the section @ref overview_container_std explaining how to do it.
25
26 Otherwise you will need to know about the custom wxWidgets container classes
27 such as wxList<T> and wxArray<T> if only to use wxWidgets functions that work
28 with them, e.g. wxWindow::GetChildren(), and you should find the information
29 about using these classes below useful.
30
31 Notice that we recommend that you use standard classes directly in your own
32 code instead of the container classes provided by wxWidgets in any case as the
33 standard classes are easier to use and may also be safer because of extra
34 run-time checks they may perform as well as more efficient.
35
36 Finally notice that recent versions of wxWidgets also provide standard-like
37 classes such as wxVector<T>, wxStack<T> or wxDList which can be used exactly
38 like the std::vector<T>, std::stack<T> and std::list<T*>, respectively, and
39 actually are just typedefs for the corresponding types if wxWidgets is compiled
40 in STL mode. These classes could be useful if you wish to avoid the use of the
41 standard library in your code for some reason.
42
43 To summarize, you should use the standard container classes such as
44 std::vector<T> and std::list<T> if possible and wxVector<T> or wxDList<T> if
45 it isn't and only use legacy wxWidgets containers such as wxArray<T> and
46 wxList<T> when you must, i.e. when you use a wxWidgets function taking or
47 returning a container of such type.
48
49
50 @section overview_container_legacy Legacy Classes
51
52 The list classes in wxWidgets are doubly-linked lists which may either own the
53 objects they contain (meaning that the list deletes the object when it is
54 removed from the list or the list itself is destroyed) or just store the
55 pointers depending on whether or not you called wxList<T>::DeleteContents()
56 method.
57
58 Dynamic arrays resemble C arrays but with two important differences: they
59 provide run-time range checking in debug builds and they automatically expand
60 the allocated memory when there is no more space for new items. They come in
61 two sorts: the "plain" arrays which store either built-in types such as "char",
62 "int" or "bool" or the pointers to arbitrary objects, or "object arrays" which
63 own the object pointers to which they store.
64
65 For the same portability reasons, the container classes implementation in
66 wxWidgets don't use templates, but are rather based on C preprocessor i.e. are
67 implemented using the macros: WX_DECLARE_LIST() and WX_DEFINE_LIST() for the
68 linked lists and WX_DECLARE_ARRAY(), WX_DECLARE_OBJARRAY() and
69 WX_DEFINE_OBJARRAY() for the dynamic arrays.
70
71 The "DECLARE" macro declares a new container class containing the elements of
72 given type and is needed for all three types of container classes: lists,
73 arrays and objarrays. The "DEFINE" classes must be inserted in your program in
74 a place where the @e full declaration of container element class is in scope
75 (i.e. not just forward declaration), otherwise destructors of the container
76 elements will not be called!
77
78 As array classes never delete the items they contain anyhow, there is no
79 WX_DEFINE_ARRAY() macro for them.
80
81 Examples of usage of these macros may be found in wxList<T> and wxArray<T>
82 documentation.
83
84 Finally, wxWidgets predefines several commonly used container classes. wxList
85 is defined for compatibility with previous versions as a list containing
86 wxObjects and wxStringList as a list of C-style strings (char *), both of these
87 classes are deprecated and should not be used in new programs. The following
88 array classes are defined: wxArrayInt, wxArrayLong, wxArrayPtrVoid and
89 wxArrayString. The first three store elements of corresponding types, but
90 wxArrayString is somewhat special: it is an optimized version of wxArray which
91 uses its knowledge about wxString reference counting schema.
92
93
94 @section overview_container_std STL Build
95
96 To build wxWidgets with the standard containers you need to set
97 wxUSE_STD_CONTAINERS option to 1 in @c wx/msw/setup.h for wxMSW builds or
98 specify @c --enable-std_containers option to configure (which is also
99 implicitly enabled by @c --enable-stl option) in Unix builds.
100
101 The standard container build is mostly, but not quite, compatible with the
102 default one. Here are the most important differences:
103 - wxList::compatibility_iterator must be used instead of wxList::Node* when
104 iterating over the list contents. The compatibility_iterator class has the
105 same semantics as a Node pointer but it is an object and not a pointer, so
106 you need to write
107 @code
108 for ( wxWindowList::compatibility_iterator it = list.GetFirst();
109 it;
110 it = it->GetNext() )
111 ...
112 @endcode
113 instead of the old
114 @code
115 for ( wxWindowList::Node *n = list.GetFirst(); n; n = n->GetNext() )
116 ...
117 @endcode
118 - wxSortedArrayString and wxArrayString are separate classes now and the
119 former doesn't derive from the latter. If you need to convert a sorted array
120 to a normal one, you must copy all the elements. Alternatively, you may
121 avoid the use of wxSortedArrayString by using a normal array and calling its
122 Sort() method when needed.
123 - WX_DEFINE_ARRAY_INT(bool) cannot be used because of the differences in
124 std::vector<bool> specialization compared with the generic std::vector<>
125 class. Please either use std::vector<bool> directly or use an integer array
126 instead.
127
128
129 */
130