Using qeventloop to realize synchronous waiting for the return of slot function

Encountered a problem in doing a project , The system is externally connected with a IO equipment , The module needs to trigger reading ,

QTcpSocket The reading of is realized by slot function , The module hopes to get the result directly through only one reading interface . It needs to be done once in the interface IO, however readyRead_Slot It's not synchronous , It can't be blocked here （ Thread attempted join The way ） Wait for , Message queues that affect signals and slots , Not achieving the desired effect . 

The test passed qeventloop Manually starting the message cycle can achieve this goal . Code up .

void rfidClient::getCurrentRFID(int &result)
{
    if(tcpSocket == NULL)
        return;

    char sbuf[7] = {0};
    sbuf[0] = 0xA0;
    sbuf[1] = 0x04;
    sbuf[2] = 0x01;
    sbuf[3] = 0x89;
    sbuf[4] = 0x01;
    sbuf[5] = 0xD1;
    sbuf[6] = '\0';

    tcpSocket->write(sbuf);

    QEventLoop* el = new QEventLoop();
    connect(this, &rfidClient::readFinished, el, &QEventLoop::quit);      //IO At the end , End the event cycle 
    connect(this, &rfidClient::readFinished, this, &rfidClient::analyData); //IO At the end , Processing return results 
    el->exec();    // Start the event cycle , wait for IO end 

    //   here analyData Have dealt with 
    if(rfidResult.size() > 0)
    {
        result = rfidResult.at(0);
    }
    else
    {
        result = -1;
    }