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。