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Re: invalid use of non-static member function

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On 1/1/2020 7:32 AM, Andrew Z wrote:
>>> OutletToggleTask is a non-static member function.
>>>
>>> As a non-static member function it takes a hidden `this` parameter,
>>> which might not be passed in the same way as other parameters. Therefore
>>> you can't convert it to pointer-to-free-function in any portable way.
>>>
>>> Additionally the construct `outlet.OutletToggleTask` is a callable
>>> expression that in itself has no type. It's silly in a very serious way:
>>> the lack of a type for it is a core language deficiency that stands in
>>> the way of easily using C++ for e.g. GUI code, or other code that
>>> requires object oriented callbacks. C# has delegates for this, and the
>>> C++ standard library has `std::function` and `std::bind`, but it really
>>> requires core language support for ease of use.
>>>
>>> One easy practical solution to your problem is to simply declare the
>>> function `static` in the class, or make it a free function.
>>>
>>>
>>> [snip]
>>>
>>> - Alf
>> There's a second problem, which is might be the one detected by the
>> compiler, although the above is definitely an error too.
>> The last argument of setup_task is expected to be an object of type
>> TickType_t, but a pointer to member function is passed instead:
>> "outlet.GetCycleTicks" should be "outlet.GetCycleTicks()"
> 
> Manfred,
>   Alf,
>   thank you for the reply.
> void setup_task(
>                  void (*DeviceTask)(void*),
>                  char* TaskName,
>                  EventGroupHandle_t eventGroup,
>                  void (*Callback_Fn)(TimerHandle_t),
>                  TickType_t cycle_ticks ) { .. }
> setup_task(
>                  outlet.OutletToggleTask,
>                  (char*)"Outlet Task",
>                  eventGroup,
>                  outlet.OutletCallback,
>                  outlet.GetCycleTicks );
> why is the outlet.GetCycleTicks is considered to be a pointer, but the eventGroup is not?

eventGroup is declared as

> EventGroupHandle_t eventGroup;

So, it is an object, not a pointer.

> 
> changing outlet.GetCycleTicks to outlet.GetCycleTicks() or a number doesn't change the compile time error. I'm still digesting what Alf said above...

This is not surprising, all of OutletToggleTask, OutletCallback and 
GetCycleTicks are non-static member functions that are used invalidly, 
although for different reasons.

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Thread

invalid use of non-static member function Andrew Z <formisc@gmail.com> - 2019-12-30 20:01 -0800
  Re: invalid use of non-static member function "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-12-31 06:34 +0100
    Re: invalid use of non-static member function Manfred <noname@add.invalid> - 2019-12-31 17:22 +0100
      Re: invalid use of non-static member function Andrew Z <formisc@gmail.com> - 2019-12-31 22:32 -0800
        Re: invalid use of non-static member function Manfred <noname@add.invalid> - 2020-01-01 18:15 +0100
          Re: invalid use of non-static member function Andrew Z <formisc@gmail.com> - 2020-01-01 18:49 -0800
    Re: invalid use of non-static member function Andrew Z <formisc@gmail.com> - 2019-12-31 23:03 -0800
      Re: invalid use of non-static member function "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2020-01-01 22:48 +0100
        Re: invalid use of non-static member function Andrew Z <formisc@gmail.com> - 2020-01-15 07:35 -0800

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