'Any' is not convertible to 'AVCaptureDevice' error translating Objective C to Swift

Question

I'm rebuilding the Google Mobile Vision "Googly Eyes" demo in Swift 3. I figured almost all of it out, but I'm stuck on translating a function from Objective C to Swift.

The Objective C function in the demo view controller is:

  - (AVCaptureDeviceInput *)cameraForPosition:(AVCaptureDevicePosition)desiredPosition {
    BOOL hadError = NO;
    for (AVCaptureDevice *device in [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]) {
      if ([device position] == desiredPosition) {
        NSError *error = nil;
        AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
                                                                            error:&error];
        if (error) {
          hadError = YES;
          NSLog(@"Could not initialize for AVMediaTypeVideo for device %@", device);
        } else if ([self.session canAddInput:input]) {
          return input;
        }
      }
    }
    if (!hadError) {
      NSLog(@"No camera found for requested orientation");
    }
    return nil;
  }

I've translated that into the following:

func camera(for desiredPosition: AVCaptureDevicePosition) -> AVCaptureDeviceInput {
    var hadError: Bool = false
    for device: AVCaptureDevice in AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo) { // ERROR ON THIS LINE
        if device.position() == desiredPosition {
            var error: Error? = nil
            let input = try? AVCaptureDeviceInput(device: device)
            if error != nil {
                hadError = true
                print("Could not initialize for AVMediaTypeVideo for device \(device)")
            }
            else if session.canAdd(input!) {
                return input!
            }
        }
    }
    if !hadError {
        print("No camera found for requested orientation")
    }
  }

The error I'm getting is on the 3rd line (for device: AVCaptureDevice in AVCaptureDevice.devices...). The error is: 'Any' is not convertible to 'AVCaptureDevice'. I'm not very familiar with Objective C and have never used AVCaptureSession before so I've been struggling to figure it out. Any suggestions on how I need to rewrite this "for device" statement?

Answer 1

Assuming you use the latest release version of Xcode. It's Xcode 8.3.3 at the time of this post.

I show you codes for some simplified cases.

---

Case 1

Continue using deprecated method (not recommended):

func camera(for desiredPosition: AVCaptureDevicePosition) -> AVCaptureDeviceInput? {
    var hadError: Bool = false
    for device in AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo) as! [AVCaptureDevice] { //### You need to cast
        if device.position == desiredPosition {
            do {
                let input = try AVCaptureDeviceInput(device: device)
                if session.canAddInput(input) { //###<-
                    return input
                }
            } catch {
                hadError = true
                print("Could not initialize for AVMediaTypeVideo for device \(device) with \(error)")
            }
        }
    }
    if !hadError {
        print("No camera found for requested orientation")
    }
    return nil
}

The return type of devices(withMediaType:) is [Any]!, so if you want to use each element as AVCaptureDevice, you need to cast it.

Similar to your code, but I fixed some parts, canAdd to canAddInput and the error handling.

---

Case 2

Use AVCaptureDeviceDiscoverySession ignoring older versions of iOS than 10.0.

func camera(for desiredPosition: AVCaptureDevicePosition) -> AVCaptureDeviceInput? {
    var hadError: Bool = false
    for device in AVCaptureDeviceDiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaTypeVideo, position: desiredPosition).devices {
        do {
            let input = try AVCaptureDeviceInput(device: device)
            if session.canAddInput(input) {
                return input
            }
        } catch {
            hadError = true
            print("Could not initialize for AVMediaTypeVideo for device \(device) with \(error)")
        }
    }
    if !hadError {
        print("No camera found for requested orientation")
    }
    return nil
}

A simple example of using AVCaptureDeviceDiscoverySession, .builtInWideAngleCamera matches for front camera, normal back camera and wide angle camera on dual camera device.

---

NOTE

Many methods in above codes have changed their signatures in Swift 4/Xcode 9, including the return type. And in iOS SDK 11, there's a nice method:

class func default(AVCaptureDevice.DeviceType, for: AVMediaType?, position: AVCaptureDevice.Position)