How to use software timer within a class?

General
1

I need to use a software timer within a class but I cannot get the code to compile.

The should work _updateTimer = new Timer(4, &myClass::update, this); as it follows the same syntax as Particle.function("control", &myClass::control, this); which does compile.

I read some other posts on the forum about using lambda to solve this issue but it seems like it should be unneccessary, plus I could not get a lambda to compile.

How should I be instantiating and using a software timer within a class so that it calls a function: void myClass::update() {...}

Thanks

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2

If you called your class MyClass…
In your header file (.h), usually in Private.

Timer* timerObj;

In Class begin() function (it is my understanding this won’t work in you class constructor because you can’t guarantee in what order objects will be instantiated.

timerObj = new Timer(50, (void (*)())&myClass::update);

To start and stop your timer (any Timer Class member function actually)

timerObj->start();
timerObj->stop();
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3

It works, thanks.

Particle need to remove the need for this or document it somewhere as it’s really not clear.

1 Like
4

Thanks for the heads up, we’ll look into adding similar class function support as exists with other callbacks in the API.

5

Hi,

I have tried the syntax listed here, but I cannot get this to compile? I get;
no matching function for call to 'Timer::Timer(int, void (Foo::*)(), Foo&)

The code in the header file is;
Class Foo{
void onTimeout();
_Timer *myTimer;
public:
Foo(int x, int y, int z);
}

and in the cpp;
Foo::Foo(int x, int y, int z){
myTimer = new Timer (x, (void (*)())&Foo::onTimeout);
}

I’m really trying to get my head around this but I am struggling with the class member functions! Any help would be appreciated!

6

Also, I have tried the code from this thread as well.
And both will not compile.

I am working on an electron project and incidentally I tried compiling for a photon and it worked???
Maybe calling member class functions is not supported on the electron?

7

You haven’t marked the class method static.
When you want to pass a method to a function that is ignorant of the object instances the method needs to be static to be resolved by the compiler.
To have non-static functions play well, the receiving function needs to learn about the instance pointer of the respective object too.

Hence there now is a dedicated function to set up an object method too
https://docs.particle.io/reference/firmware/photon/#class-member-callbacks

Hence try this in your .cpp

myTimer = new Timer (x, &Foo::onTimeout, *this);
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8

Thanks @ScruffR
I gave that a crack but I still get an error;

The error seems to be the ‘this’ so maybe the timers are not allowed to be class members?
I have tried the code from the docs, and that works fine as a non class member but it doesn’t work as soon as it is a class member.with the ‘this’.

9

Yup, I forgot the deref asterisk :blush: (added above now)

Try this one

class Foo {
private:
    Timer t1 = Timer(1000, &Foo::cb, *this);
    Timer t2;

public:
    Foo() : t2(Timer(2000, &Foo::cb, *this)) { 
    }

    void begin() {
        t1.start();
        t2.start();
    } 

    void cb() { 
    }

};

Foo f;
void setup()
{
  f.begin();    
}
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10

It compiles! :grinning:

You have no idea how long I have spent trying to get that to work! Legend :+1:

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