self.device  = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    self.input   = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:nil];

    self.output  = [[AVCaptureMetadataOutput alloc] init];

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

     self.session = [[AVCaptureSession alloc] init];

    [self.session setSessionPreset:AVCaptureSessionPresetHigh];

     if ([self.session canAddInput:self.input])

    {

        [self.session addInput:self.input];

    }

    if ([self.session canAddOutput:self.output])

    {

        [self.session addOutput:self.output];

    }

    // 扫码类型

    self.output.metadataObjectTypes = @[AVMetadataObjectTypeQRCode];

    self.preview = [AVCaptureVideoPreviewLayer layerWithSession:self.session];

    self.preview.videoGravity = AVLayerVideoGravityResizeaspectFill;

    self.preview.frame = self.view.layer.bounds;

    [self.view.layer insertSublayer:self.preview atIndex:0];

     [self.session startRunning];

这儿是扫码成功之后调用的代理方法

#pragma mark AVCaptureMetadataOutputObjectsDelegate

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection

{

    NSString *stringValue;

    if ([metadataObjects count] >0)

    {

        //停止扫描

        [_session stopRunning];

        AVMetadataMachineReadableCodeObject * metadataObject = [metadataObjects objectAtIndex:0];

        stringValue = metadataObject.stringValue;

    }

    NSLog(@" %@",stringValue);

    // 获取到二维码的数据之后的后续操作

}