C++ (Qt)
class SomeClass : public QObject
{
    Q_OBJECT
public:
    explicit SomeClass(QObject *parent = 0);
 
signals:
    void workSignal();
 
public slots:
    void work();
    void nonBlockWork();
 
};

C++ (Qt)
SomeClass::SomeClass(QObject *parent) :
    QObject(parent)
{
    connect(this, SIGNAL(workSignal()), this, SLOT(work()));
}
 
void SomeClass::work()
{
}
 
void SomeClass::nonBlockWork()
{
    emit workSignal();
}

C++ (Qt)
myThread = new MyThread( this );
connect ( ui->pushButton, SIGNAL( clicked() ), muThread, SLOT( doWork() ), Qt::QueuedConnection );
myThread->start();

C++ (Qt)
Scanner scanner(this);
scanner.scan() // получаем не блокирующий вызов, который выполняется в отдельном потоке и не тормозит основной.

C++ (Qt)
class CScaner: public QThread
{
public:
 
	CScaner( QObject * parent = 0):QThread(parent)
	{
	}
 
	void scan()
	{
		start(QThread::NormalPriority);
	};
 
//...
 
protected:
	virtual void run()
	{
		reallyLongMethod();
		emit image(/*...*/);
	}
private:
 
	void reallyLongMethod()
	{
	// ....
	}	
};
 
CMyWidget::foo()
{
	CScaner* scaner = new CScaner(this);
	scaner->deleteLater();
	connect(scaner, SIGNAL(image(/*...*/)), this, SLOT(setImageScan(/*....*/)));
	connect(scaner, SIGNAL(finished()), scaner, SLOT(deleteLater());	
}