Qt Core学习日记——第七天QMetaObject（上）

每一个声明Q_OBJECT的类都具有QMetaObject对象

Q_OBJECT宏源代码：

#define Q_OBJECT \

public: \

QT_WARNING_PUSH \

Q_OBJECT_NO_OVERRIDE_WARNING \

static const QMetaObject staticMetaObject; \

virtual const QMetaObject *metaObject() const; \

virtual void *qt_metacast(const char *); \

virtual int qt_metacall(QMetaObject::Call, int, void **); \

QT_TR_FUNCTIONS \

private: \

Q_OBJECT_NO_ATTRIBUTES_WARNING \

Q_DECL_HIDDEN_STATIC_METACALL static void qt_static_metacall(QObject *, QMetaObject::Call, int, void **); \

QT_WARNING_POP \

struct QPrivateSignal {}; \

QT_ANNOTATE_CLASS(qt_qobject, "")

每一个声明Q_OBJECT类的对象都具有同一静态成员staticMetaObject，staticMetaObject用于存储类的基础信息，比如类属性、类信息。

例如类XTest的QMetaObject staticMetaObject

XTest::staticMetaObject中包含类信息"author", "Sabrina Schweinsteiger"，类属性autoStartup，槽函数、信号、其它函数

XTest.h

#pragma once

#include <qobject.h>

#include <QFlags>

class XTest : public QObject

{

Q_OBJECT

Q_CLASSINFO("author", "Sabrina Schweinsteiger")

Q_PROPERTY(bool autoStartup READ autoStartup WRITE setAutoStartup NOTIFY sigAutoStartup)

public:

XTest(QObject* p = nullptr) {}

~XTest() {}

public:

enum Priority

{

High,

Low,

VeryHigh,

VeryLow

};

Q_ENUM(Priority)

enum PriorityFlag

{

High1,

Low1,

VeryHigh1,

VeryLow1

};

Q_FLAG(PriorityFlag)

Q_DECLARE_FLAGS(Alignment, PriorityFlag)

Q_FLAG(Alignment)

public:

bool autoStartup() { return m_autoStartup; }

void setAutoStartup(bool b) { m_autoStartup = b; emit sigAutoStartup(); }

public slots:

void slot1(double* p1) {}

Q_INVOKABLE void slot2(int* p2) {}

Q_REVISION(1) void slot3(char* p3) {}

Q_INVOKABLE void slot4(int p2, double) {}

signals:

void sig1(void * p4);

void sigAutoStartup();

private:

Q_REVISION(1) bool m_autoStartup = false;

};

XTest.cpp:

#include "XTest.h"

qt生成的moc文件moc_XTest.cpp:

/****************************************************************************

** Meta object code from reading C++ file 'XTest.h'

**

** Created by: The Qt Meta Object Compiler version 67 (Qt 5.15.2)

**

** WARNING! All changes made in this file will be lost!

*****************************************************************************/

#include <memory>

#include "../../../XTest.h"

#include <QtCore/qbytearray.h>

#include <QtCore/qmetatype.h>

#if !defined(Q_MOC_OUTPUT_REVISION)

#error "The header file 'XTest.h' doesn't include <QObject>."

#elif Q_MOC_OUTPUT_REVISION != 67

#error "This file was generated using the moc from 5.15.2. It"

#error "cannot be used with the include files from this version of Qt."

#error "(The moc has changed too much.)"

#endif

QT_BEGIN_MOC_NAMESPACE

QT_WARNING_PUSH

QT_WARNING_DISABLE_DEPRECATED

struct qt_meta_stringdata_XTest_t {

QByteArrayData data[29];

char stringdata0[212];

};

#define QT_MOC_LITERAL(idx, ofs, len) \

Q_STATIC_BYTE_ARRAY_DATA_HEADER_INITIALIZER_WITH_OFFSET(len, \

qptrdiff(offsetof(qt_meta_stringdata_XTest_t, stringdata0) + ofs \

- idx * sizeof(QByteArrayData)) \

)

static const qt_meta_stringdata_XTest_t qt_meta_stringdata_XTest = {

{

QT_MOC_LITERAL(0, 0, 5), // "XTest"

QT_MOC_LITERAL(1, 6, 6), // "author"

QT_MOC_LITERAL(2, 13, 22), // "Sabrina Schweinsteiger"

QT_MOC_LITERAL(3, 36, 4), // "sig1"

QT_MOC_LITERAL(4, 41, 0), // ""

QT_MOC_LITERAL(5, 42, 2), // "p4"

QT_MOC_LITERAL(6, 45, 14), // "sigAutoStartup"

QT_MOC_LITERAL(7, 60, 5), // "slot1"

QT_MOC_LITERAL(8, 66, 7), // "double*"

QT_MOC_LITERAL(9, 74, 2), // "p1"

QT_MOC_LITERAL(10, 77, 5), // "slot2"

QT_MOC_LITERAL(11, 83, 4), // "int*"

QT_MOC_LITERAL(12, 88, 2), // "p2"

QT_MOC_LITERAL(13, 91, 5), // "slot3"

QT_MOC_LITERAL(14, 97, 5), // "char*"

QT_MOC_LITERAL(15, 103, 2), // "p3"

QT_MOC_LITERAL(16, 106, 5), // "slot4"

QT_MOC_LITERAL(17, 112, 11), // "autoStartup"

QT_MOC_LITERAL(18, 124, 8), // "Priority"

QT_MOC_LITERAL(19, 133, 4), // "High"

QT_MOC_LITERAL(20, 138, 3), // "Low"

QT_MOC_LITERAL(21, 142, 8), // "VeryHigh"

QT_MOC_LITERAL(22, 151, 7), // "VeryLow"

QT_MOC_LITERAL(23, 159, 12), // "PriorityFlag"

QT_MOC_LITERAL(24, 172, 5), // "High1"

QT_MOC_LITERAL(25, 178, 4), // "Low1"

QT_MOC_LITERAL(26, 183, 9), // "VeryHigh1"

QT_MOC_LITERAL(27, 193, 8), // "VeryLow1"

QT_MOC_LITERAL(28, 202, 9) // "Alignment"

},

"XTest\0author\0Sabrina Schweinsteiger\0"

"sig1\0\0p4\0sigAutoStartup\0slot1\0double*\0"

"p1\0slot2\0int*\0p2\0slot3\0char*\0p3\0slot4\0"

"autoStartup\0Priority\0High\0Low\0VeryHigh\0"

"VeryLow\0PriorityFlag\0High1\0Low1\0"

"VeryHigh1\0VeryLow1\0Alignment"

};

#undef QT_MOC_LITERAL

static const uint qt_meta_data_XTest[] = {

// content:

8, // revision

0, // classname

1, 14, // classinfo

6, 16, // methods

1, 70, // properties

3, 74, // enums/sets

0, 0, // constructors

0, // flags

2, // signalCount

// classinfo: key, value

1, 2,

// signals: name, argc, parameters, tag, flags

3, 1, 52, 4, 0x06 /* Public */,

6, 0, 55, 4, 0x06 /* Public */,

// slots: name, argc, parameters, tag, flags

7, 1, 56, 4, 0x0a /* Public */,

10, 1, 59, 4, 0x0a /* Public */,

13, 1, 62, 4, 0x8a /* Public | MethodRevisioned */,

16, 2, 65, 4, 0x0a /* Public */,

// signals: revision

0,

0,

// slots: revision

0,

0,

1,

0,

// signals: parameters

QMetaType::Void, QMetaType::VoidStar, 5,

QMetaType::Void,

// slots: parameters

QMetaType::Void, 0x80000000 | 8, 9,

QMetaType::Void, 0x80000000 | 11, 12,

QMetaType::Void, 0x80000000 | 14, 15,

QMetaType::Void, QMetaType::Int, QMetaType::Double, 12, 4,

// properties: name, type, flags

17, QMetaType::Bool, 0x00495103,

// properties: notify_signal_id

1,

// enums: name, alias, flags, count, data

18, 18, 0x0, 4, 89,

23, 23, 0x1, 4, 97,

28, 23, 0x1, 4, 105,

// enum data: key, value

19, uint(XTest::High),

20, uint(XTest::Low),

21, uint(XTest::VeryHigh),

22, uint(XTest::VeryLow),

24, uint(XTest::High1),

25, uint(XTest::Low1),

26, uint(XTest::VeryHigh1),

27, uint(XTest::VeryLow1),

24, uint(XTest::High1),

25, uint(XTest::Low1),

26, uint(XTest::VeryHigh1),

27, uint(XTest::VeryLow1),

0 // eod

};

void XTest::qt_static_metacall(QObject *_o, QMetaObject::Call _c, int _id, void **_a)

{

if (_c == QMetaObject::InvokeMetaMethod) {

auto *_t = static_cast<XTest *>(_o);

Q_UNUSED(_t)

switch (_id) {

case 0: _t->sig1((*reinterpret_cast< void*(*)>(_a[1]))); break;

case 1: _t->sigAutoStartup(); break;

case 2: _t->slot1((*reinterpret_cast< double*(*)>(_a[1]))); break;

case 3: _t->slot2((*reinterpret_cast< int*(*)>(_a[1]))); break;

case 4: _t->slot3((*reinterpret_cast< char*(*)>(_a[1]))); break;

case 5: _t->slot4((*reinterpret_cast< int(*)>(_a[1])),(*reinterpret_cast< double(*)>(_a[2]))); break;

default: ;

}

} else if (_c == QMetaObject::IndexOfMethod) {

int *result = reinterpret_cast<int *>(_a[0]);

{

using _t = void (XTest::*)(void * );

if (*reinterpret_cast<_t *>(_a[1]) == static_cast<_t>(&XTest::sig1)) {

*result = 0;

return;

}

}

{

using _t = void (XTest::*)();

if (*reinterpret_cast<_t *>(_a[1]) == static_cast<_t>(&XTest::sigAutoStartup)) {

*result = 1;

return;

}

}

}

#ifndef QT_NO_PROPERTIES

else if (_c == QMetaObject::ReadProperty) {

auto *_t = static_cast<XTest *>(_o);

Q_UNUSED(_t)

void *_v = _a[0];

switch (_id) {

case 0: *reinterpret_cast< bool*>(_v) = _t->autoStartup(); break;

default: break;

}

} else if (_c == QMetaObject::WriteProperty) {

auto *_t = static_cast<XTest *>(_o);

Q_UNUSED(_t)

void *_v = _a[0];

switch (_id) {

case 0: _t->setAutoStartup(*reinterpret_cast< bool*>(_v)); break;

default: break;

}

} else if (_c == QMetaObject::ResetProperty) {

}

#endif // QT_NO_PROPERTIES

}

QT_INIT_METAOBJECT const QMetaObject XTest::staticMetaObject = { {

QMetaObject::SuperData::link<QObject::staticMetaObject>(),

qt_meta_stringdata_XTest.data,

qt_meta_data_XTest,

qt_static_metacall,

nullptr,

nullptr

} };

const QMetaObject *XTest::metaObject() const

{

return QObject::d_ptr->metaObject ? QObject::d_ptr->dynamicMetaObject() : &staticMetaObject;

}

void *XTest::qt_metacast(const char *_clname)

{

if (!_clname) return nullptr;

if (!strcmp(_clname, qt_meta_stringdata_XTest.stringdata0))

return static_cast<void*>(this);

return QObject::qt_metacast(_clname);

}

int XTest::qt_metacall(QMetaObject::Call _c, int _id, void **_a)

{

_id = QObject::qt_metacall(_c, _id, _a);

if (_id < 0)

return _id;

if (_c == QMetaObject::InvokeMetaMethod) {

if (_id < 6)

qt_static_metacall(this, _c, _id, _a);

_id -= 6;

} else if (_c == QMetaObject::RegisterMethodArgumentMetaType) {

if (_id < 6)

*reinterpret_cast<int*>(_a[0]) = -1;

_id -= 6;

}

#ifndef QT_NO_PROPERTIES

else if (_c == QMetaObject::ReadProperty || _c == QMetaObject::WriteProperty

|| _c == QMetaObject::ResetProperty || _c == QMetaObject::RegisterPropertyMetaType) {

qt_static_metacall(this, _c, _id, _a);

_id -= 1;

} else if (_c == QMetaObject::QueryPropertyDesignable) {

_id -= 1;

} else if (_c == QMetaObject::QueryPropertyScriptable) {

_id -= 1;

} else if (_c == QMetaObject::QueryPropertyStored) {

_id -= 1;

} else if (_c == QMetaObject::QueryPropertyEditable) {

_id -= 1;

} else if (_c == QMetaObject::QueryPropertyUser) {

_id -= 1;

}

#endif // QT_NO_PROPERTIES

return _id;

}

// SIGNAL 0

void XTest::sig1(void * _t1)

{

void *_a[] = { nullptr, const_cast<void*>(reinterpret_cast<const void*>(std::addressof(_t1))) };

QMetaObject::activate(this, &staticMetaObject, 0, _a);

}

// SIGNAL 1

void XTest::sigAutoStartup()

{

QMetaObject::activate(this, &staticMetaObject, 1, nullptr);

}

QT_WARNING_POP

QT_END_MOC_NAMESPACE

函数解析：

静态函数

bool QMetaObject::checkConnectArgs(const char *signal, const char *method)

检查2个字符串参数是否相同。传入参数字符串需要是QMetaObject::normalizedSignature返回的字符串。例如slots2函数签名是“slots2(int*)”。就是上一篇QMetaMethod::methodSignature函数返回值

bool QMetaObject::checkConnectArgs(const QMetaMethod &signal, const QMetaMethod &method)

检查信号与槽参数连接参数是否相同

QByteArray QMetaObject::normalizedSignature

获取函数签名。例如slots2函数签名是“slots2(int*)”。就是上一篇QMetaMethod::methodSignature函数返回值