WinUI3 : How to use DispatcherQueue without Lambda function to exec a parameterized function

Harshithraj1871 1,516

Hi,

Im working on a WinUI3 desktop application in CPP without using XAML files.

In my application, I'm using the Dispatcher queue to switch from the worker thread to the main thread.

int winid = 1;

DispatcherQueueHandler      executeinstructiondispatch = [=] () {	TWOSInstructionHandler::ExecuteInstructionSet (winid);
}

TWWinUI3App::sDispatcherQueue.TryEnqueue (executeinstructiondispatchhandler);

Here to execute a parameterized function in the main thread, Im using the Lambda function.

For some reason, I do not want to use any Lambda functions in my application. Is there any way to make this peace of code work without the Lambda function?

I could have done this if it was not a parameterized function,

DispatcherQueueHandler      executeinstructiondispatch = TWOSInstructionHandler::ExecuteInstructionSet;

In the case of a parameterized function, is there a way to use Dispatcher Queue without the lambda function?

Thank you

Xiaopo Yang - MSFT 12,151 Microsoft Vendor

Do you mean this?

        winrt::Microsoft::UI::Dispatching::DispatcherQueueHandler h = [](){};

        std::function<void()> f = []() {};
        winrt::Microsoft::UI::Dispatching::DispatcherQueueHandler h2 = std::bind(&FirstPage::myTest,this,1);

        this->DispatcherQueue().TryEnqueue(Microsoft::UI::Dispatching::DispatcherQueuePriority::Normal,f);
        this->DispatcherQueue().TryEnqueue(Microsoft::UI::Dispatching::DispatcherQueuePriority::Normal,h);
        this->DispatcherQueue().TryEnqueue(Microsoft::UI::Dispatching::DispatcherQueuePriority::Normal,h2);

Harshithraj1871 1,516 Reputation points

2023-11-17T09:58:09.2166667+00:00

Yes, thank you, @Xiaopo Yang - MSFT , Is there a way to do the same without std functions?

Xiaopo Yang - MSFT 12,151 Microsoft Vendor

You can only use member functions with no parameters.

        template <typename O, typename M> DispatcherQueueHandler(O* object, M method);
        template <typename O, typename M> DispatcherQueueHandler(com_ptr<O>&& object, M method);
        template <typename O, typename M> DispatcherQueueHandler(weak_ref<O>&& object, M method);

winrt::Microsoft::UI::Dispatching::DispatcherQueueHandler h3 = {this, &FirstPage::myTest1};

    void FirstPage::myTest1()
    {

    }

Or you can implement a simple class with operator()() by yourself.

Harshithraj1871 1,516 Reputation points

2023-11-20T04:59:21.5533333+00:00

Can we do the same for parameterized functions?
Xiaopo Yang - MSFT 12,151 Reputation points Microsoft Vendor

2023-11-20T05:12:55.8333333+00:00

NO, you need to implement your class with operator()() if not use std.
Harshithraj1871 1,516 Reputation points

2023-11-20T05:34:30.5733333+00:00

Okay, I can't see how overloading the "()" operator will help to pass parameters. Can you give an example
Xiaopo Yang - MSFT 12,151 Reputation points Microsoft Vendor

2023-11-20T06:08:54.87+00:00

See https://gist.github.com/Redchards/c5be14c2998f1ca1d757 for an example.
Harshithraj1871 1,516 Reputation points

2023-11-28T08:44:04.86+00:00

Okay, thank you
Xiaopo Yang - MSFT 12,151 Reputation points Microsoft Vendor

2023-11-29T01:48:41.4433333+00:00

@Harshithraj1871, now that do you consider completing the question?

Accepted answer

Xiaopo Yang - MSFT 12,151 Reputation points Microsoft Vendor

2023-11-28T08:14:04.2833333+00:00

As far as I'm concerned, it's not supported for C++/WinRT to enable passing functions with parameters. You can also use a Lambda function to wrap these functions except std::bind.
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