Setup camera capture and view on iOS (and flip camera + flashlight)

AVCaptureSession Example

// *** Setup camera *** //
- (void)setupCamera
{
    // setup session
    self.session = [AVCaptureSession new];
    self.session.sessionPreset = AVCaptureSessionPresetPhoto;
    
    // setup device
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    if ([device lockForConfiguration:nil]) {
        if (device.autoFocusRangeRestrictionSupported) {
            device.autoFocusRangeRestriction = AVCaptureAutoFocusRangeRestrictionNear;
        }
        
        if (device.smoothAutoFocusSupported) {
            device.smoothAutoFocusEnabled = YES;
        }
        
        if ([device isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus]){
            device.focusMode = AVCaptureFocusModeContinuousAutoFocus;
        }
        
        device.exposureMode = AVCaptureExposureModeContinuousAutoExposure;
        
        [device unlockForConfiguration];
    }
    
    // add device input to session
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    [self.session addInput:deviceInput];
    
    // add output to session
    NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecJPEG, AVVideoCodecKey, nil];
    AVCaptureStillImageOutput *stillImage = [AVCaptureStillImageOutput new];
    stillImage.outputSettings = outputSettings;
    [self.session addOutput:stillImage];
    
    AVCaptureVideoPreviewLayer *preview = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
    preview.videoGravity = AVLayerVideoGravityResizeAspectFill;
    preview.frame = self.cameraPreview.layer.bounds;
    [self.cameraPreview.layer addSublayer:preview];
    
    [self.session startRunning];
}

// *** Flip camera *** //
//Change camera source
- (IBAction)flipTapped:(id)sender
{
    //Change camera source
    if(self.session)
    {
        //Indicate that some changes will be made to the session
        [self.session beginConfiguration];
        
        //Remove existing input
        AVCaptureInput* currentCameraInput = [self.session.inputs objectAtIndex:0];
        [self.session removeInput:currentCameraInput];
        
        //Get new input
        AVCaptureDevice *newCamera = nil;
        if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack) {
            newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
        }
        else {
            newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
        }
        
        //Add input to session
        NSError *err = nil;
        AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];
        if(!newVideoInput || err) {
            NSLog(@"Error creating capture device input: %@", err.localizedDescription);
        }
        else {
            [self.session addInput:newVideoInput];
        }
        
        //Commit all the configuration changes at once
        [self.session commitConfiguration];
    }
}

- (AVCaptureDevice *) cameraWithPosition:(AVCaptureDevicePosition) position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if ([device position] == position) return device;
    }
    return nil;
}

- (IBAction)flashTapped:(id)sender
{
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (device.hasTorch) {
        [device lockForConfiguration:nil];
        if (device.torchMode == AVCaptureTorchModeOn) {
            device.torchMode = AVCaptureTorchModeOff;
        } else {
            [device setTorchModeOnWithLevel:AVCaptureMaxAvailableTorchLevel error:nil];
        }
    }
}