iOS implements QR code scanning function

//
// 
// QRCode
//
// Created by chenchen on 15/7/30.
// Copyright (c) 2015 BSY. All rights reserved.//
#import <AVFoundation/>
#import ""
@interface ViewController ()<AVCaptureMetadataOutputObjectsDelegate>
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
  [super viewDidLoad];
  
   
   
  AVCaptureSession *session = [[AVCaptureSession alloc] init];
  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];
  //Set the encoding format supported by scanning code (set the barcode and QR code compatible as follows)  [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode,AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code]];
  [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
  [session addOutput:output];
  [session startRunning];
}
 
#pragma mark - AVCaptureMetadataOutputObjectsDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputMetadataObjects:(NSArray *)metadataObjects
    fromConnection:(AVCaptureConnection *)connection
{
  NSString *QRCode = nil;
  for (AVMetadataObject *metadata in metadataObjects) {
    if ([ isEqualToString:AVMetadataObjectTypeQRCode]) {
      // This will never happen; nobody has ever scanned a QR code... ever
      QRCode = [(AVMetadataMachineReadableCodeObject *)metadata stringValue];
      break;
    }
  }
   
  NSLog(@"QR Code: %@", QRCode);
}
- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}
 
@end