Use Qt's reflection mechanism to obtain the relevant information of the written class (the number of class member functions, type, name, etc., with example code)

I recently studied the reflection mechanism of
Qt. In addition to the characteristics of the signal/slot mechanism provided by Qt's meta-object system, it also provides the following characteristics:

QObject::metaObject()
returns the associated meta object

QMetaObject::className()
returns the class name in runtime state

QObject::inherits()
determines the inheritance relationship of a class

QObject::tr(), QObject::trUtf8()
provide internationalization, translation strings

QObject::setProperty(), QObject::property()
to dynamically set and get properties by name

QMetaObject::newInstance()
creates a new instance

Through the QObject::metaObject() method, all classes that inherit from QObject can return the metaObject object generated for them by the meta-object system. Some important information provided by QMetaObject:

QMetaClassInfo
provides additional information about the class through the support of the macro Q_CLASSINFO

QMetaEnum
Qt's characteristic enumeration object, which supports mutual conversion between key and value

QMetaMethod
provides metadata for class member functions

QMetaProperty
provides metadata for class member properties

Qt反射前期准备
1、首先得继承于Q_Object，同时需要在class中加入Q_OBJECT。
2、注册类成员变量需要使用Q_PROPERTY
Q_PROPERTY( type member READ get WRITE set) 其中READ，WRITE是关键字
Type表示成员的类型（不支持自定义类型，对Qt很多基本类型都支持）;
Member代表你给该成员另外起的名字，可以和变量名不同；get，set就是自己在C++函数里面定义的基本的访问函数名，不需要写参数。

3、注册类成员函数
如果你希望这个函数能够被反射，那么很简单，只需要在类的函数声明前加入Q_INVOKABLE关键字。
参考文章：
blog.csdn.net/playstudy/a…
www.cnblogs.com/RainyBear/p…

下面是我自己编写的实例：
1.右击QT Creater中的项目名——添加新文件——选择C++ Class——Choose——取个Class name：TestClass——Base Class选择QObject——点击下一步——在项目文件列表中会增加一个testclass.h和testclass.cpp
testclass.h中如下：

#ifndef TESTCLASS_H
#define TESTCLASS_H
#include <QObject>
class TestClass : public QObject
{
    Q_OBJECT
public:
    explicit TestClass(QObject *parent = 0);
    Q_INVOKABLE int sum(int na,int nb);
    Q_INVOKABLE int decrease(int na, int nb);
signals:
public slots:
};
#endif // TESTCLASS_H
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testclass.cpp中如下：

#include "testclass.h"
    TestClass::TestClass(QObject *parent) : QObject(parent)
    {
    
    }
    int TestClass::sum(int na,int nb)
    {
        return na+nb;
    }
    int TestClass::decrease(int na, int nb)
    {
        return na-nb;
    }
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在主界面的cpp中添加一个按钮响应函数，如下：
注：在主界面.cpp中要包含TestClass的头文件#include “testClass.h”

void MainWindow::on_ShowClassInfo_clicked()
{
    TestClass classTestClass;
    const QMetaObject *theMetaObject = classTestClass.metaObject();//定义一个QMetaObject对象指针，用来获取类classTestClass的相关信息
    int nMetathodCount = theMetaObject->methodCount();
    for(int nMetathodIndex = 0;nMetathodIndex < nMetathodCount;nMetathodIndex++)
    {
        QMetaMethod oneMethod = theMetaObject->method(nMetathodIndex);
        qDebug() <<"MethodName: " <<oneMethod.name();
        qDebug() <<"parameterNames: " <<oneMethod.parameterNames();
        qDebug()<<"parameterTypes" << oneMethod.parameterTypes();
        qDebug() <<"typeName: " <<oneMethod.typeName();
        qDebug() <<"signature: " <<oneMethod.Signal;
        qDebug() <<"methodType: " <<oneMethod.methodType() <<"\n";
    }
}
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程序运行后，点击ShowClassInfo按钮，在“应用程序输出”界面会显示如下信息：

MethodName:  "destroyed"
parameterNames:  ("")
parameterTypes ("QObject*")
typeName:  void
signature:  1
methodType:  1 

MethodName:  "destroyed"
parameterNames:  ()
parameterTypes ()
typeName:  void
signature:  1
methodType:  1 

MethodName:  "objectNameChanged"
parameterNames:  ("objectName")
parameterTypes ("QString")
typeName:  void
signature:  1
methodType:  1 

MethodName:  "deleteLater"
parameterNames:  ()
parameterTypes ()
typeName:  void
signature:  1
methodType:  2 

MethodName:  "_q_reregisterTimers"
parameterNames:  ("")
parameterTypes ("void*")
typeName:  void
signature:  1
methodType:  2 

MethodName:  "sum"
parameterNames:  ("na", "nb")
parameterTypes ("int", "int")
typeName:  int
signature:  1
methodType:  0 

MethodName:  "decrease"
parameterNames:  ("na", "nb")
parameterTypes ("int", "int")
typeName:  int
signature:  1
methodType:  0 
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可以看到，TestClass实例化的类变量classTestClass的QMetaObject遍历出来的QMetaMethod一共有7个，其中除了我们手动添加的int sum(int na,int nb);和int decrease(int na, int nb);之外，还有5个自动生成的隐藏的QMetaMethod。