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39
40#include "qscopedpointer.h"
41
42QT_BEGIN_NAMESPACE
43
44/*!
45 \class QScopedPointer
46 \inmodule QtCore
47 \brief The QScopedPointer class stores a pointer to a dynamically allocated object, and deletes it upon destruction.
48 \since 4.6
49 \reentrant
50 \ingroup misc
51
52 Managing heap allocated objects manually is hard and error prone, with the
53 common result that code leaks memory and is hard to maintain.
54 QScopedPointer is a small utility class that heavily simplifies this by
55 assigning stack-based memory ownership to heap allocations, more generally
56 called resource acquisition is initialization(RAII).
57
58 QScopedPointer guarantees that the object pointed to will get deleted when
59 the current scope disappears.
60
61 Consider this function which does heap allocations, and has various exit points:
62
63 \snippet code/src_corelib_tools_qscopedpointer.cpp 0
64
65 It's encumbered by the manual delete calls. With QScopedPointer, the code
66 can be simplified to:
67
68 \snippet code/src_corelib_tools_qscopedpointer.cpp 1
69
70 The code the compiler generates for QScopedPointer is the same as when
71 writing it manually. Code that makes use of \a delete are candidates for
72 QScopedPointer usage (and if not, possibly another type of smart pointer
73 such as QSharedPointer). QScopedPointer intentionally has no copy
74 constructor or assignment operator, such that ownership and lifetime is
75 clearly communicated.
76
77 The const qualification on a regular C++ pointer can also be expressed with
78 a QScopedPointer:
79
80 \snippet code/src_corelib_tools_qscopedpointer.cpp 2
81
82 \section1 Custom Cleanup Handlers
83
84 Arrays as well as pointers that have been allocated with \c malloc must
85 not be deleted using \c delete. QScopedPointer's second template parameter
86 can be used for custom cleanup handlers.
87
88 The following custom cleanup handlers exist:
89
90 \list
91 \li QScopedPointerDeleter - the default, deletes the pointer using \c delete
92 \li QScopedPointerArrayDeleter - deletes the pointer using \c{delete []}. Use
93 this handler for pointers that were allocated with \c{new []}.
94 \li QScopedPointerPodDeleter - deletes the pointer using \c{free()}. Use this
95 handler for pointers that were allocated with \c{malloc()}.
96 \li QScopedPointerDeleteLater - deletes a pointer by calling \c{deleteLater()}
97 on it. Use this handler for pointers to QObject's that are actively
98 participating in a QEventLoop.
99 \endlist
100
101 You can pass your own classes as handlers, provided that they have a public
102 static function \c{void cleanup(T *pointer)}.
103
104 \snippet code/src_corelib_tools_qscopedpointer.cpp 5
105
106 \section1 Forward Declared Pointers
107
108 Classes that are forward declared can be used within QScopedPointer, as
109 long as the destructor of the forward declared class is available whenever
110 a QScopedPointer needs to clean up.
111
112 Concretely, this means that all classes containing a QScopedPointer that
113 points to a forward declared class must have non-inline constructors,
114 destructors and assignment operators:
115
116 \snippet code/src_corelib_tools_qscopedpointer.cpp 4
117
118 Otherwise, the compiler outputs a warning about not being able to destruct
119 \c MyPrivateClass.
120
121 \sa QSharedPointer
122*/
123
124/*! \typedef QScopedPointer::pointer
125 \internal
126 */
127
128/*!
129 \fn template <typename T, typename Cleanup> QScopedPointer<T, Cleanup>::QScopedPointer(T *p = 0)
130
131 Constructs this QScopedPointer instance and sets its pointer to \a p.
132*/
133
134/*!
135 \fn template <typename T, typename Cleanup> QScopedPointer<T, Cleanup>::~QScopedPointer()
136
137 Destroys this QScopedPointer object. Delete the object its pointer points
138 to.
139*/
140
141/*!
142 \fn template <typename T, typename Cleanup> T *QScopedPointer<T, Cleanup>::data() const
143
144 Returns the value of the pointer referenced by this object. QScopedPointer
145 still owns the object pointed to.
146*/
147
148/*!
149 \fn template <typename T, typename Cleanup> T *QScopedPointer<T, Cleanup>::get() const
150 \since 5.11
151
152 Same as data().
153*/
154
155/*!
156 \fn template <typename T, typename Cleanup> T &QScopedPointer<T, Cleanup>::operator*() const
157
158 Provides access to the scoped pointer's object.
159
160 If the contained pointer is \nullptr, behavior is undefined.
161 \sa isNull()
162*/
163
164/*!
165 \fn template <typename T, typename Cleanup> T *QScopedPointer<T, Cleanup>::operator->() const
166
167 Provides access to the scoped pointer's object.
168
169 If the contained pointer is \nullptr, behavior is undefined.
170
171 \sa isNull()
172*/
173
174/*!
175 \fn template <typename T, typename Cleanup> QScopedPointer<T, Cleanup>::operator bool() const
176
177 Returns \c true if the contained pointer is not \nullptr.
178 This function is suitable for use in \tt if-constructs, like:
179
180 \snippet code/src_corelib_tools_qscopedpointer.cpp 3
181
182 \sa isNull()
183*/
184
185/*!
186 \fn template <typename T, typename Cleanup> bool operator==(const QScopedPointer<T, Cleanup> &lhs, const QScopedPointer<T, Cleanup> &rhs)
187
188 Returns \c true if \a ptr1 and \a ptr2 refer to the same pointer.
189*/
190
191
192/*!
193 \fn template <typename T, typename Cleanup> bool operator!=(const QScopedPointer<T, Cleanup> &lhs, const QScopedPointer<T, Cleanup> &rhs)
194
195 Returns \c true if \a lhs and \a rhs refer to distinct pointers.
196*/
197
198/*!
199 \fn template <typename T, typename Cleanup> bool operator==(const QScopedPointer<T, Cleanup> &lhs, std::nullptr_t)
200 \relates QScopedPointer
201 \since 5.8
202
203 Returns \c true if \a lhs refers to \nullptr.
204
205 \sa QScopedPointer::isNull()
206*/
207
208/*!
209 \fn template <typename T, typename Cleanup> bool operator==(std::nullptr_t, const QScopedPointer<T, Cleanup> &rhs)
210 \relates QScopedPointer
211 \since 5.8
212
213 Returns \c true if \a rhs refers to \nullptr.
214
215 \sa QScopedPointer::isNull()
216*/
217
218/*!
219 \fn template <typename T, typename Cleanup> bool operator!=(const QScopedPointer<T, Cleanup> &lhs, std::nullptr_t)
220 \relates QScopedPointer
221 \since 5.8
222
223 Returns \c true if \a lhs refers to a valid (i.e. non-null) pointer.
224
225 \sa QScopedPointer::isNull()
226*/
227
228/*!
229 \fn template <typename T, typename Cleanup> bool operator!=(std::nullptr_t, const QScopedPointer<T, Cleanup> &rhs)
230 \relates QScopedPointer
231 \since 5.8
232
233 Returns \c true if \a rhs refers to a valid (i.e. non-null) pointer.
234
235 \sa QScopedPointer::isNull()
236*/
237
238/*!
239 \fn template <typename T, typename Cleanup> bool QScopedPointer<T, Cleanup>::isNull() const
240
241 Returns \c true if this object refers to \nullptr.
242*/
243
244/*!
245 \fn template <typename T, typename Cleanup> void QScopedPointer<T, Cleanup>::reset(T *other = 0)
246
247 Deletes the existing object it is pointing to (if any), and sets its pointer to
248 \a other. QScopedPointer now owns \a other and will delete it in its
249 destructor.
250
251 To clear the pointer held without deleting the object it points to (and hence take ownership
252 of the object), use \l take() instead.
253*/
254
255/*!
256 \fn template <typename T, typename Cleanup> T *QScopedPointer<T, Cleanup>::take()
257
258 Returns the value of the pointer referenced by this object. The pointer of this
259 QScopedPointer object will be reset to \nullptr.
260
261 Callers of this function take ownership of the pointer.
262*/
263
264/*! \fn template <typename T, typename Cleanup> bool QScopedPointer<T, Cleanup>::operator!() const
265
266 Returns \c true if this object refers to \nullptr.
267
268 \sa isNull()
269*/
270
271/*! \fn template <typename T, typename Cleanup> void QScopedPointer<T, Cleanup>::swap(QScopedPointer<T, Cleanup> &other)
272 Swap this pointer with \a other.
273 */
274
275/*!
276 \class QScopedArrayPointer
277 \inmodule QtCore
278
279 \brief The QScopedArrayPointer class stores a pointer to a
280 dynamically allocated array of objects, and deletes it upon
281 destruction.
282
283 \since 4.6
284 \reentrant
285 \ingroup misc
286
287 A QScopedArrayPointer is a QScopedPointer that defaults to
288 deleting the object it is pointing to with the delete[] operator. It
289 also features operator[] for convenience, so we can write:
290
291 \code
292 void foo()
293 {
294 QScopedArrayPointer<int> i(new int[10]);
295 i[2] = 42;
296 ...
297 return; // our integer array is now deleted using delete[]
298 }
299 \endcode
300*/
301
302/*!
303 \fn template <typename T, typename Cleanup> QScopedArrayPointer<T, Cleanup>::QScopedArrayPointer()
304
305 Constructs a QScopedArrayPointer instance.
306*/
307
308/*!
309 \fn template <typename T, typename Cleanup> template <typename D> QScopedArrayPointer<T, Cleanup>::QScopedArrayPointer(D * p)
310
311 Constructs a QScopedArrayPointer and stores the array of objects
312 pointed to by \a p.
313*/
314
315/*!
316 \fn template <typename T, typename Cleanup> T *QScopedArrayPointer<T, Cleanup>::operator[](int i)
317
318 Provides access to entry \a i of the scoped pointer's array of
319 objects.
320
321 If the contained pointer is \nullptr, behavior is undefined.
322
323 \sa isNull()
324*/
325
326/*!
327 \fn template <typename T, typename Cleanup> T *QScopedArrayPointer<T, Cleanup>::operator[](int i) const
328
329 Provides access to entry \a i of the scoped pointer's array of
330 objects.
331
332 If the contained pointer is \nullptr behavior is undefined.
333
334 \sa isNull()
335*/
336
337/*! \fn template <typename T, typename Cleanup> void QScopedArrayPointer<T, Cleanup>::swap(QScopedArrayPointer<T, Cleanup> &other)
338 Swap this pointer with \a other.
339 */
340
341QT_END_NAMESPACE
342

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