编译就是通不过，不知道为啥

#include
#include
using std::cout;
using std::endl;

class Employee : public QObject
{
    Q_OBJECT
public:
    Employee(int);
    int getSalary() const;
signals:
    void salaryChanged(int);
public slots:
    void setSalary(int);
private:
    int salary;
};

Employee::Employee(int salary)
{
    this->salary = salary;
    connect(this,SIGNAL(salaryChanged(int)),this,SLOT(setSalary(int)));
}

int Employee::getSalary() const
{
    return salary;
}

void Employee::setSalary(int newSalary)
{
    if(newSalary != salary)
    {
        salary = newSalary;
        emit salaryChanged(newSalary);
    }
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    Employee e(3200);
    e.setSalary(4500);

    return a.exec();
}