summaryrefslogtreecommitdiffstats
path: root/src/corelib/doc/snippets/code/src_corelib_kernel_qobject.cpp
blob: 6451f46b363e1deaa889d3d25a65af6e37d2c52b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/

//! [1]
QObject *obj = new QPushButton;
obj->metaObject()->className();             // returns "QPushButton"

QPushButton::staticMetaObject.className();  // returns "QPushButton"
//! [1]


//! [2]
QPushButton::staticMetaObject.className();  // returns "QPushButton"

QObject *obj = new QPushButton;
obj->metaObject()->className();             // returns "QPushButton"
//! [2]


//! [3]
QObject *obj = new QTimer;          // QTimer inherits QObject

QTimer *timer = qobject_cast<QTimer *>(obj);
// timer == (QObject *)obj

QAbstractButton *button = qobject_cast<QAbstractButton *>(obj);
// button == 0
//! [3]


//! [4]
QTimer *timer = new QTimer;         // QTimer inherits QObject
timer->inherits("QTimer");          // returns true
timer->inherits("QObject");         // returns true
timer->inherits("QAbstractButton"); // returns false

// QVBoxLayout inherits QObject and QLayoutItem
QVBoxLayout *layout = new QVBoxLayout;
layout->inherits("QObject");        // returns true
layout->inherits("QLayoutItem");    // returns true (even though QLayoutItem is not a QObject)
//! [4]


//! [5]
qDebug("MyClass::setPrecision(): (%s) invalid precision %f",
       qPrintable(objectName()), newPrecision);
//! [5]


//! [6]
class MainWindow : public QMainWindow
{
public:
    MainWindow();

protected:
    bool eventFilter(QObject *obj, QEvent *ev) override;

private:
    QTextEdit *textEdit;
};

MainWindow::MainWindow()
{
    textEdit = new QTextEdit;
    setCentralWidget(textEdit);

    textEdit->installEventFilter(this);
}

bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
    if (obj == textEdit) {
        if (event->type() == QEvent::KeyPress) {
            QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
            qDebug() << "Ate key press" << keyEvent->key();
            return true;
        } else {
            return false;
        }
    } else {
        // pass the event on to the parent class
        return QMainWindow::eventFilter(obj, event);
    }
}
//! [6]


//! [7]
myObject->moveToThread(QApplication::instance()->thread());
//! [7]


//! [8]
class MyObject : public QObject
{
    Q_OBJECT

public:
    MyObject(QObject *parent = 0);

protected:
    void timerEvent(QTimerEvent *event) override;
};

MyObject::MyObject(QObject *parent)
    : QObject(parent)
{
    startTimer(50);     // 50-millisecond timer
    startTimer(1000);   // 1-second timer
    startTimer(60000);  // 1-minute timer

    using namespace std::chrono;
    startTimer(milliseconds(50));
    startTimer(seconds(1));
    startTimer(minutes(1));

    // since C++14 we can use std::chrono::duration literals, e.g.:
    startTimer(100ms);
    startTimer(5s);
    startTimer(2min);
    startTimer(1h);
}

void MyObject::timerEvent(QTimerEvent *event)
{
    qDebug() << "Timer ID:" << event->timerId();
}
//! [8]


//! [9]
QList<QObject *> list = window()->queryList("QAbstractButton"));
foreach (QObject *obj, list)
    static_cast<QAbstractButton *>(obj)->setEnabled(false);
//! [9]


//! [10]
QPushButton *button = parentWidget->findChild<QPushButton *>("button1");
//! [10]


//! [11]
QListWidget *list = parentWidget->findChild<QListWidget *>();
//! [11]


//! [12]
QList<QWidget *> widgets = parentWidget.findChildren<QWidget *>("widgetname");
//! [12]


//! [13]
QList<QPushButton *> allPButtons = parentWidget.findChildren<QPushButton *>();
//! [13]


//! [14]
monitoredObj->installEventFilter(filterObj);
//! [14]


//! [15]
class KeyPressEater : public QObject
{
    Q_OBJECT
    ...

protected:
    bool eventFilter(QObject *obj, QEvent *event) override;
};

bool KeyPressEater::eventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::KeyPress) {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
        qDebug("Ate key press %d", keyEvent->key());
        return true;
    } else {
        // standard event processing
        return QObject::eventFilter(obj, event);
    }
}
//! [15]


//! [16]
KeyPressEater *keyPressEater = new KeyPressEater(this);
QPushButton *pushButton = new QPushButton(this);
QListView *listView = new QListView(this);

pushButton->installEventFilter(keyPressEater);
listView->installEventFilter(keyPressEater);
//! [16]


//! [17]
MyWindow::MyWindow()
{
    QLabel *senderLabel = new QLabel(tr("Name:"));
    QLabel *recipientLabel = new QLabel(tr("Name:", "recipient"));
//! [17]
}


//! [18]
int n = messages.count();
showMessage(tr("%n message(s) saved", "", n));
//! [18]


//! [19]
n == 1 ? tr("%n message saved") : tr("%n messages saved")
//! [19]


//! [20]
label->setText(tr("F\374r \310lise"));
//! [20]


//! [21]
if (receivers(SIGNAL(valueChanged(QByteArray))) > 0) {
    QByteArray data;
    get_the_value(&data);       // expensive operation
    emit valueChanged(data);
}
//! [21]


//! [22]
QLabel *label = new QLabel;
QScrollBar *scrollBar = new QScrollBar;
QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
                 label,  SLOT(setNum(int)));
//! [22]


//! [23]
// WRONG
QObject::connect(scrollBar, SIGNAL(valueChanged(int value)),
                 label, SLOT(setNum(int value)));
//! [23]


//! [24]
class MyWidget : public QWidget
{
    Q_OBJECT

public:
    MyWidget();

signals:
    void buttonClicked();

private:
    QPushButton *myButton;
};

MyWidget::MyWidget()
{
    myButton = new QPushButton(this);
    connect(myButton, SIGNAL(clicked()),
            this, SIGNAL(buttonClicked()));
}
//! [24]


//! [25]
QObject::connect: Cannot queue arguments of type 'MyType'
(Make sure 'MyType' is registered using qRegisterMetaType().)
//! [25]


//! [26]
disconnect(myObject, 0, 0, 0);
//! [26]


//! [27]
myObject->disconnect();
//! [27]


//! [28]
disconnect(myObject, SIGNAL(mySignal()), 0, 0);
//! [28]


//! [29]
myObject->disconnect(SIGNAL(mySignal()));
//! [29]


//! [30]
disconnect(myObject, 0, myReceiver, 0);
//! [30]


//! [31]
myObject->disconnect(myReceiver);
//! [31]


//! [32]
if (signal == QMetaMethod::fromSignal(&MyObject::valueChanged)) {
    // signal is valueChanged
}
//! [32]


//! [33]
void on_<object name>_<signal name>(<signal parameters>);
//! [33]


//! [34]
void on_button1_clicked();
//! [34]


//! [35]
class MyClass : public QObject
{
    Q_OBJECT
    Q_CLASSINFO("Author", "Pierre Gendron")
    Q_CLASSINFO("URL", "http://www.my-organization.qc.ca")

public:
    ...
};
//! [35]

//! [37]
Q_PROPERTY(QString title READ title WRITE setTitle USER true)
//! [37]


//! [38]
class MyClass : public QObject
{
    Q_OBJECT

public:
    MyClass(QObject *parent = 0);
    ~MyClass();

    enum Priority { High, Low, VeryHigh, VeryLow };
    Q_ENUM(Priority)
    void setPriority(Priority priority);
    Priority priority() const;
};
//! [38]


//! [39]
class QLibrary : public QObject
{
    Q_OBJECT

public:
    ...

    enum LoadHint {
        ResolveAllSymbolsHint = 0x01,
        ExportExternalSymbolsHint = 0x02,
        LoadArchiveMemberHint = 0x04
    };
    Q_DECLARE_FLAGS(LoadHints, LoadHint)
    Q_FLAG(LoadHints)
    ...
}
//! [39]


//! [40]
//: This name refers to a host name.
hostNameLabel->setText(tr("Name:"));

/*: This text refers to a C++ code example. */
QString example = tr("Example");
//! [40]

//! [41]
QPushButton *button = parentWidget->findChild<QPushButton *>("button1", Qt::FindDirectChildrenOnly);
//! [41]


//! [42]
QListWidget *list = parentWidget->findChild<QListWidget *>(QString(), Qt::FindDirectChildrenOnly);
//! [42]


//! [43]
QList<QPushButton *> childButtons = parentWidget.findChildren<QPushButton *>(QString(), Qt::FindDirectChildrenOnly);
//! [43]

//! [44]
QLabel *label = new QLabel;
QLineEdit *lineEdit = new QLineEdit;
QObject::connect(lineEdit, &QLineEdit::textChanged,
                 label,  &QLabel::setText);
//! [44]

//! [45]
void someFunction();
QPushButton *button = new QPushButton;
QObject::connect(button, &QPushButton::clicked, someFunction);
//! [45]

//! [46]
QByteArray page = ...;
QTcpSocket *socket = new QTcpSocket;
socket->connectToHost("qt-project.org", 80);
QObject::connect(socket, &QTcpSocket::connected, [=] () {
        socket->write("GET " + page + "\r\n");
    });
//! [46]

//! [47]
disconnect(myObject, &MyObject::mySignal(), 0, 0);
//! [47]

//! [48]
QObject::disconnect(lineEdit, &QLineEdit::textChanged,
                 label,  &QLabel::setText);
//! [48]

//! [49]
static const QMetaMethod valueChangedSignal = QMetaMethod::fromSignal(&MyObject::valueChanged);
if (isSignalConnected(valueChangedSignal)) {
    QByteArray data;
    data = get_the_value();       // expensive operation
    emit valueChanged(data);
}
//! [49]

//! [50]
void someFunction();
QPushButton *button = new QPushButton;
QObject::connect(button, &QPushButton::clicked, this, someFunction, Qt::QueuedConnection);
//! [50]

//! [51]
QByteArray page = ...;
QTcpSocket *socket = new QTcpSocket;
socket->connectToHost("qt-project.org", 80);
QObject::connect(socket, &QTcpSocket::connected, this, [=] () {
        socket->write("GET " + page + "\r\n");
    }, Qt::AutoConnection);
//! [51]

//! [52]
class MyClass : public QWidget
{
    Q_OBJECT

public:
    MyClass(QWidget *parent = 0);
    ~MyClass();

    bool event(QEvent* ev) override
    {
        if (ev->type() == QEvent::PolishRequest) {
            // overwrite handling of PolishRequest if any
            doThings();
            return true;
        } else  if (ev->type() == QEvent::Show) {
            // complement handling of Show if any
            doThings2();
            QWidget::event(ev);
            return true;
        }
        // Make sure the rest of events are handled
        return QWidget::event(ev);
    }
};
//! [52]

//! [meta data]
//: This is a comment for the translator.
//= qtn_foo_bar
//~ loc-layout_id foo_dialog
//~ loc-blank False
//~ magic-stuff This might mean something magic.
QString text = MyMagicClass::tr("Sim sala bim.");
//! [meta data]

//! [explicit tr context]
QString text = QScrollBar::tr("Page up");
//! [explicit tr context]