Define scanCompleteCB with using std::function

[asukiaaa]

I want to use bind for scanCompleteCB like this.

class Controller {
  void startScan() {
    scanning = true;
    auto pScan = NimBLEDevice::getScan();
    pScan->setAdvertisedDeviceCallbacks(advDeviceCBs);
    pScan->setInterval(45);
    pScan->setWindow(15);
    Serial.println("Start scan");
    // pScan->start(scanTime, scanEndedCB);
    pScan->start(scanTime,
                 std::bind(&Core::scanEndedCB, this, std::placeholders::_1)); // <<<<<<<<<< ======== Here
  }

  void scanEndedCB(NimBLEScanResults results) {
    Serial.println("Scan Ended");
    scanning = false;
  }
};

Related issue: #342

[h2zero]

Sorry for the delay.

This is a good idea but we have a problem.

This will break the API for users that do not provide the is_continue parameter when they provide a callback that does not use std::bind (such as the examples). In this scenario the callback argument is converted to a bool(true) by the compiler and results in calling the wrong start() method, and the callback is not called.

In order to support this correctly another solution is needed. If we are going to break the API, I think the best way would be to have a setScanEndCallback method or a callback class added to NimBLEScan and remove the function parameter from the start calls. This would also require renaming the start() method to support the blocking and non-blocking calls with different naming.

I'm open to other suggestions, this is just my first thoughts.

Note: merging this will need to wait until the other breaking changes I have in mind are implemented with the upcoming 2.0 releases.

[asukiaaa]

Thank you for the response.
I understand that this change breaks current code.

have a setScanEndCallback method or a callback class added to NimBLEScan

I agree passing a class instance for a function because we can support additional callback easily.

I have in mind are implemented with the upcoming 2.0 releases.

I see, thanks.

[h2zero]

@asukiaaa Please take a look at #389, it is part of a few breaking changes I have planned for a version 2 release and should suit your needs.

[asukiaaa]

Thank you for updating but it seems renaming m_pAdvertisedDeviceCallbacks to m_pScanCallbacks and reuse it as m_scanCompleteCB.
Is it possible to distinguish the timing of finding some device and finishing scanning?

[h2zero]

Sorry, I need to update an examples to make it clearer. The advertised device callback class has been replaced with the scan callback class which contains the virtual function onResult and onScanEnd that you can define for your needs.

[asukiaaa]

Thank you for the explanation.
I could use the updated NimBLE without using global(static?) functions and variables.
asukiaaa/arduino-XboxSeriesXControllerESP32@57e50c1

[h2zero]

You got it 😄

[asukiaaa]

This request is satisfied by onScanEnd callback on #389.
Thank you.