scanForPeripheralsWithServices:return result twice on the same peripheral

Question

I use the below code

[centralManager scanForPeripheralsWithServices:serviceUUIDArray 
         options:[NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] 
         forKey:CBCentralManagerScanOptionAllowDuplicatesKey]]

to scan a perpheral device, then the result return twice on the same peripheral. How to return one? Thanks.

Filter by UUID... Drop it if it doen't have one yet (still not given) — Larme, Aug 21 '13 at 08:51
UUID is available on the peripheral only if it had been connected before. New peripherals don't have UUIDs. Filtering the ones with `nil` UUID out would effectively disable finding new peripherals. — allprog, Aug 21 '13 at 20:43

score 2 · Answer 1 · answered Aug 21 '13 at 20:41

This is happening because the peripheral's name is updated. In this case you get the callback once more.

This thread contains a detailed explanation: http://lists.apple.com/archives/bluetooth-dev/2013/Apr/msg00099.html

Credits go to Etan Kissling:

The device name is cached by iOS according to a priority list:

Name read from Device name characteristic after a connect

Name from advertising packet

null

Note that the name from the advertising packet should be a prefix of the final name in the Device name characteristic.

Maybe the physical device already had the name cached, and does not send the second update, as it already retrieved the name.

Your app should be able to deal with duplicates even when you don't request them.

To deal with duplicates, you can check the already received ones with the isEqualTo: method on the peripheral or use an NSSet for storing them.

@Etan Are you kidding? I even gave you reps for it. – allprog Oct 25 '13 at 11:30 — allprog, Oct 25 '13 at 11:30
@Etan , you're the best! (To clarify my comment above.) – allprog Oct 25 '13 at 17:48 — allprog, Oct 25 '13 at 17:48

scanForPeripheralsWithServices:return result twice on the same peripheral

1 Answers1