AVCaptureMetadataOutputObjectsDelegate not called in swift 4 for QR scanner

Question

I was working on QR code scanner app on iOS where i was getting output AVCaptureOutput on the delegate method captureOutput:didOutputMetadataObjects:fromConnection:.

It was working perfectly on swift 3. After I've updated to xcode 9 and swift 4, it stopped working.

score 18 · Accepted Answer · answered Oct 09 '17 at 06:01

18

Okay I've found an update here.

Found that AVCaptureMetadataOutputObjectsDelegate method is changed

from

captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!)

to

metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection)

After changing this delegate method, its working good now.

answered Oct 09 '17 at 06:01

Arnab

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Note that the signature of this method changed (again..) after converting to Swift 4 - and it is not detected / fixed by the automatic migration - unlike other camera related callbacks. – GK100 Dec 04 '17 at 20:55
1

Thank you for this! What's bizarre is that the compiler did not complain that I was missing the protocol's function implementation because the function is marked `optional`. Considering this is the only method in this protocol to implement, I do not think it should be `optional`. – John Rogers Mar 13 '18 at 03:34

score 2 · Answer 2 · answered Apr 23 '19 at 09:43

in Swift 4:

Replace

let metadataOutput = AVCaptureMetadataOutput()
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
metadataOutput.metadataObjectTypes = metadataOutput.availableMetadataObjectTypes

With:

let metadataOutput = AVCaptureMetadataOutput()
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
let supportedCodeTypes = [AVMetadataObject.ObjectType.upce,
                          AVMetadataObject.ObjectType.code39,
                          AVMetadataObject.ObjectType.code39Mod43,
                          AVMetadataObject.ObjectType.code93,
                          AVMetadataObject.ObjectType.code128,
                          AVMetadataObject.ObjectType.ean8,
                          AVMetadataObject.ObjectType.ean13,
                          AVMetadataObject.ObjectType.aztec,
                          AVMetadataObject.ObjectType.pdf417,
                          AVMetadataObject.ObjectType.qr]

metadataOutput.metadataObjectTypes = supportedCodeTypes

AVCaptureMetadataOutputObjectsDelegate not called in swift 4 for QR scanner

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