Qt 信号和槽 一

Qt 信号和槽 分析一

#ifndef COUNTER_H
#define COUNTER_H

#include <QObject>

class counter : public QObject
{
Q_OBJECT
public:
explicit counter(QObject *parent = 0);
int value() const;
private:
int m_value;

signals:
void valuechange(int);
public slots:
void setvalue(int);

};

#endif // COUNTER_H

#include "counter.h"
#include <iostream>
using namespace std;

counter::counter(QObject *parent) :
    QObject(parent)
{
    m_value=0;
}

int counter::value() const
{
    
    return m_value;
}

void counter::setvalue(int newvalue)
{
    if(m_value!=newvalue)
    {
        m_value=newvalue;
        emit valuechange(newvalue);
    }
}

#include <QtCore/QCoreApplication>
#include "counter.h"
#include <iostream>
using namespace std;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    counter app1,app2;
    QObject::connect(&app1,SIGNAL(valuechange(int)),&app2,SLOT(setvalue(int)));
    app1.setvalue(12);
    cout<<app1.value()<<" "<<app2.value()<<endl;
    app2.setvalue(24);
    cout<<app1.value()<<" "<<app2.value()<<endl;
    return a.exec();
}