用于条件绑定的 Swift Initializer 必须具有 Optional 类型，而不是“[AVCaptureDevice]”

Question

I have this following code in my swift project

if let availabeDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone,
.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices {

            captureDevice = availabeDevices.first
        }

When i run this code it gives me an error on if line that reads:

Initializer for conditional binding must have Optional type, not '[AVCaptureDevice]'

I tried adding ? after .devices ,but that gave this error:

Cannot use optional chaining on non-optional value of type '[AVCaptureDevice]'

What do i do?

Answer 1

Use below lines.

if let captureDevice = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone, .builtInWideAngleCamera], 
mediaType: AVMediaType.video, 
position: .back).devices.first {
            self.captureDevice = captureDevice
        }

Answer 2

Explaining your error here:

You are getting error because AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone, .builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices returns [AVCaptureDevice] which is not Optional and if you want to use if let then RHS should be always Optional .

if you want to get rid of this error you need to make AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone, .builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices as Optional by adding as? [AVCaptureDevice] as? [AVCaptureDevice] at the end of it.

And your code will be:

if let availabeDevices = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInMicrophone,
                                                                            .builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back).devices as? [AVCaptureDevice] {

    let captureDevice = availabeDevices.first
}