스캔 기능(CR코드, 바코드)

 #import 

- (void)setupScaner {
    // 
    _captureSession = [[AVCaptureSession alloc]init];
    // 
    AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:nil];
    [_captureSession addInput:input];
    // 
    AVCaptureMetadataOutput *captureMetadataOutput = [[AVCaptureMetadataOutput alloc] init];
    [_captureSession addOutput:captureMetadataOutput];
    // （ ),ps: ， 
    [captureMetadataOutput setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    [captureMetadataOutput setMetadataObjectTypes:[NSArray arrayWithObjects:AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code, nil]];
    // ( capture layer )
    AVCaptureVideoPreviewLayer *videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];
    [videoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [videoPreviewLayer setFrame:self.view.layer.bounds];
    [self.view.layer addSublayer:videoPreviewLayer];
    // 
    [_captureSession startRunning];
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    if (metadataObjects != nil && [metadataObjects count] > 0) {
        AVMetadataMachineReadableCodeObject *metadataObj =[metadataObjects objectAtIndex:0];
        //metadataObj.stringValue ，  
        // nesting popViewController gif 
    }
}