how to add a 1 second delay using Qtimer

Question

I currently have a method which is as follows

void SomeMethod(int a)
{

     //Delay for one sec.
     timer->start(1000);

     //After one sec
     SomeOtherFunction(a);
}

This method is actually a slot that is attached to a signal. I would like to add a delay of one sec using Qtimer.However I am not sure on how to accomplish this. Since the timer triggers a signal when its finished and the signal would need to be attached to another method that does not take in any parameters. Any suggestion on how I could accomplish this task.?

Update : The signal will be called multiple times in a second and the delay will be for a second. My issue here is passing a parameter to the slot attached to timeout() signal of a timer. My last approach would be to store the value in a memeber variable of a class and then use a mutex to protect it from being changed while the variable is being used .however I am looking for simpler methods here.

Answer 1

Actually, there is a much more elegant solution to your question that doesn't require member variables or queues. With Qt 5.4 and C++11 you can run a Lambda expression right from the QTimer::singleShot(..) method! If you are using Qt 5.0 - 5.3 you can use the connect method to connect the QTimer's timeout signal to a Lambda expression that will call the method that needs to be delayed with the appropriate parameter.

Edit: With the Qt 5.4 release it's just one line of code!

Qt 5.4 (and later)

void MyClass::SomeMethod(int a) {
  QTimer::singleShot(1000, []() { SomeOtherFunction(a); } );
}

Qt 5.0 - 5.3

void MyClass::SomeMethod(int a) {
  QTimer *timer = new QTimer(this);
  timer->setSingleShot(true);

  connect(timer, &QTimer::timeout, [=]() {
    SomeOtherFunction(a);
    timer->deleteLater();
  } );

  timer->start(1000);
}