如何使用iOS中的Objective C在AVCaptureVideoPreviewLayer的特定区域扫描条形码？

#import <AVFoundation/AVFoundation.h>

AVCaptureSession *session = [[AVCaptureSession alloc] init];
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (input) {
    [session addInput:input];
} else {
    NSLog(@"Error: %@", error);
}

AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
[session addOutput:output];

[output setMetadataObjectTypes:@[AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code]];

CGRect scanRect = CGRectMake(x, y, width, height); // 设置扫描区域的坐标和大小
CGRect interestRect = [previewLayer metadataOutputRectOfInterestForRect:scanRect];
output.rectOfInterest = interestRect;

[output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];

- (void)captureOutput:(AVCaptureOutput *)output didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    for (AVMetadataObject *metadata in metadataObjects) {
        if ([metadata.type isEqualToString:AVMetadataObjectTypeEAN13Code]) {
            AVMetadataMachineReadableCodeObject *codeObject = (AVMetadataMachineReadableCodeObject *)[previewLayer transformedMetadataObjectForMetadataObject:metadata];
            NSLog(@"扫描到的条形码：%@", codeObject.stringValue);
        }
    }
}

previewLayer.frame = self.view.bounds;
[self.view.layer addSublayer:previewLayer];