Qt connect（）没有QObject或插槽

Question

I know what I am trying to achieve is possible, because I can do it with a lambda expression and I have done it before (Few months ago I just don't remember the syntax). Basically, I want to connect a function to a timer/button/etc. to facilitate the workings of an event.

Here is my working code:

connect( &renderTimer, &QTimer::timeout, [ = ]() {
        onTimerUpdate();
    } );

That uses a lambda to connect to the slot. I want to just reference the function itself instead of using a lambda expression. I have tried inserting the method onTimerUpdate() and &onTimerUpdate none of which work. I don't want to use QObject or any of it's pre-generated bullcrap — nor do I want to define slots within my class. I want to, quite simply, connect it directly to my function.

Answer 1

This is the format when connecting to a member function:

QObject::connect(&renderTimer, &QTimer::timeout, this, &ArclightGLWidget::onTimerUpdate); 

This is the format when connecting to a free funciton (same for lambda)

QObject::connect(&renderTimer, &QTimer::timeout, onTimerUpdate); 

And this is the format when connecting to a static member function:

QObject::connect(&renderTimer, &QTimer::timeout, SomeType::onTimerUpdate); 

Answer 2

Presumably this call is being made inside the class of which onTimerUpdate is a method. If so you can call:

connect(&renderTimer, &QTimer::timeout, this, &foo::onTimerUpdate); 

This is preferable to the lambda because Qt will manage the connection and you will also be able to call sender() in the slot .

However if you are within the class in which onTimerUpdate is a method you can also use the lambda exactly as you have put in the question:

connect( &renderTimer, &QTimer::timeout, [=](){onTimerUpdate();} );