Manually calling an Event Handler Function? Topic is solved

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tuk1
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Manually calling an Event Handler Function?

Post by tuk1 » Mon Jun 04, 2018 3:34 pm

I want to reuse the code within an event handler function and wondering the best way to go..

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EVT_BUTTON( ID_BUTTON, MAIN_FRAME::OnButtonClick )

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void MAIN_FRAME::OnButtonClick( wxCommandEvent& WXUNUSED( event ) )
{
              >>>>> Reusuable code
}

Call the function via wx event handler system?
this->GetEventHandler()->AddPendingEvent( wxCommandEvent( wxEVT_COMMAND_BUTTON_CLICKED, ID_BUTTON ) );


or

Call the function directly?
this->OnButtonClick( wxCommandEvent( wxEVT_COMMAND_BUTTON_CLICKED, ID_BUTTON ) );

Can you say the reason why with your answer.

Thanks!
Last edited by tuk1 on Mon Jun 04, 2018 5:13 pm, edited 3 times in total.
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PB
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Re: Manually calling an Event Handler Function?

Post by PB » Mon Jun 04, 2018 4:10 pm

The usual way is having a separate function that can be called from anywhere including an event handler. Calling event handler directly may not be the best choice. I.e.

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void MAIN_FRAME::DoSomething()
{
...
}


void MAIN_FRAME::OnButtonClick( wxCommandEvent& WXUNUSED( event ) )
{
	DoSomething();
}


tuk1
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Re: Manually calling an Event Handler Function?

Post by tuk1 » Mon Jun 04, 2018 4:26 pm

I was hoping to avoid adding any extra functions.

What is the problem with adding/creating the event manually or calling the handler function directly as shown in the OP?
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coderrc
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Re: Manually calling an Event Handler Function?

Post by coderrc » Mon Jun 04, 2018 5:22 pm

for multi-thread signaling I use QueueEvent so that the UI functions get called from the UI thread.

If its all on the same thread, then I will either call the function directly with a dummy parameter, or do what PB suggests. For me the choice depends on whether or not the code in question does any work with UI elements. If it does UI work, I dont want to invite the possibility of invoking a UI function from a non UI thread. I also prefer to separate GUI logic from non-gui logic as much as possible.

ONEEYEMAN
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Re: Manually calling an Event Handler Function?

Post by ONEEYEMAN » Mon Jun 04, 2018 9:24 pm

Hi,
Why you want to avoid a function? This is a normal C++ (and C for that matter) practice...
Besides, this is re-usable code. You might just call it from somewhere else - a place which doesn't need to do an event and doesn't care about an event.

Thank you.

tuk1
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Re: Manually calling an Event Handler Function?

Post by tuk1 » Tue Jun 05, 2018 9:20 am

Lets say we have an event handler function which clears the Model data when a user hits the Clear Button:

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void MAIN_FRAME::OnButtonClick_ClearModelData( wxCommandEvent& WXUNUSED( event ) )
{
	//---------------- | CLEAR LOG DATA |---------------- 

	........................
	........................
	Clear Model Data
}
And, we have 3 other event handler functions, which react to different events and do different stuff, but also want to clear the Model Data as part of their work.

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void MAIN_FRAME::OnSomeEvent1( wxCommandEvent& WXUNUSED( event ) )
{
	//---------------- | CLEAR LOG DATA |---------------- 

	........................
	........................
	Clear Model Data
}
void MAIN_FRAME::OnSomeEvent2( wxCommandEvent& WXUNUSED( event ) )
void MAIN_FRAME::OnSomeEvent3( wxCommandEvent& WXUNUSED( event ) )
---

Yes, we could have a separate, non-handler function which does the work of actually clearing the Model data, this function can then be called by any event handler functions or any other UI functions that need to clear the Model data:

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void MAIN_FRAME::Clear_Model( )
My aversion to this design is because it essentially duplicates the purpose of OnButtonClick_ClearModelData(), implementing 2 functions which do the same task, I'm not convinced this is good coding practice, adding proxy functions makes the source page longer and more complicated than it has to be.

....if we already have a function that does the task we need, then why not just call that function, thus re-using existing code instead of adding unnecessary complexity? The handler function can be called directly or via the event handler system by manually pushing an event.

If we're going to add complexity to our code we should have a good reason for doing so, right?

Is this essentially a style issue or is there a technical reason for going one way or the other?
Last edited by tuk1 on Tue Jun 05, 2018 9:25 am, edited 1 time in total.
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PB
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Re: Manually calling an Event Handler Function?

Post by PB » Tue Jun 05, 2018 9:24 am

The purpose of an event handler is to handle a specific event. You generally do not call such a function to do other things, it would imply bad code design. In contrast, you use event handlers to call a function that performs a task and which can be called from multiple places.

tuk1
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Re: Manually calling an Event Handler Function?

Post by tuk1 » Tue Jun 05, 2018 11:53 am

PB wrote:The purpose of an event handler is to handle a specific event. You generally do not call such a function to do other things, it would imply bad code design. In contrast, you use event handlers to call a function that performs a task and which can be called from multiple places.
Ok, I'm sold..
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