AVCaptureMetadataOutputObjects Wrapper

With iOS7, Apple introduced AVCaptureMetadataOutputObjects, which is used for scanning barcodes. If you check out the web for how to scan barcodes in iOS, almost everyone is talking about ZBarSDK. And before iOS7, this was definitely the way to go. But as of iOS7, ZBarSDK has a pretty nasty memory leak, and it's a big library to include when you consider barcode scanning functionality is already built into iOS7. Moreover, I consider Apple's approach to be a slightly easier than ZBarSDK was anyway.

But I decided to make it even easier. I'm working on a wrapper class that will turn several lines of code into just a few lines.

NHGBarcodeScanner.h

#import 
#import 

typedef NS_OPTIONS(unsigned short, BarcodeType) {
    CODE_UPCE           = 1 
@required - (void)barcodeScannerDidScan:(NSString*)result;
@optional - (void)barcodeInitDidFailWithError:(NSError*)error;
@end

@interface NHGBarcodeScanner : UIView

@property (nonatomic,assign) id delegate;

- (id)init __attribute__((unavailable()));
- (id)initWithFrame:(CGRect)frame __attribute__((unavailable()));

- (id)initWithFrame:(CGRect)frame barcodeTypes:(BarcodeType)barcodeTypes
                                      delegate:(id)delegate;

+ (instancetype)nhgBarcodeScannerWithFrame:(CGRect)frame 
                              barcodeTypes:(BarcodeType)barcodeTypes 
                                  delegate:(id)delegate;

- (void)startScanning;

@end

NHGBarcodeScanner.m

```
#import "NHGBarcodeScanner.h"

@interface NHGBarcodeScanner()

@end

@implementation NHGBarcodeScanner {
AVCaptureSession *_captureSession;
NSArray *_barcodeTypes;
}

+ (instancetype)nhgBarcodeScannerWithFrame:(CGRect)frame
barcodeTypes:(BarcodeType)barcodeTypes
delegate:(id)delegate {
return [[self alloc] initWithFrame:frame barcodeTypes:barcodeTypes delegate:delegate];
}

• (id)initWithFrame:(CGRect)frame

barcodeTypes:(BarcodeType)barcodeTypes

One possible improvement for the sake of convenience could be to add some meta groups to the enum.

For example:

typedef NS_OPTIONS(unsigned short, BarcodeType) {
    CODE_UPCE               = 1 << 0,
    CODE_CODE39             = 1 << 1,
    CODE_CODE39MOD43        = 1 << 2,
    CODE_EAN13              = 1 << 3,
    CODE_EAN8               = 1 << 4,
    CODE_CODE93             = 1 << 5,
    CODE_CODE128            = 1 << 6,
    CODE_PDF417             = 1 << 7,
    CODE_QRCODE             = 1 << 8,
    CODE_AZTEC              = 1 << 9
}

typedef NS_OPTIONS(unsigned short, BarcodeGroup) {
    CODEGROUP_1DBarcodes    = 1 << 0
                            + 1 << 1
                            + 1 << 2
                            + 1 << 3
                            + 1 << 4
                            + 1 << 5
                            + 1 << 6

    CODEGROUP_2DBarcodes    = 1 << 7
                            + 1 << 8
                            + 1 << 9

    CODEGROUP_ALLBarcodes   = 1 << 0
                            + 1 << 1
                            + 1 << 2
                            + 1 << 3
                            + 1 << 4
                            + 1 << 5
                            + 1 << 6
                            + 1 << 7
                            + 1 << 8
                            + 1 << 9
};

Now instead of combining large groups with the |, a user could instead simply call one of these code groups if they needed all, or just 1d codes or just 2d codes.

What's also potentially missing is a way to grab multiple codes in a batch. AVCaptureMetadataOutput will capture as many barcodes as you put in front of it all at once. It puts all these symbols into an array, and then your forin loops in the delegate method grab a single one of these codes.

There are two potential ways of sending the multiple codes.

• The delegate method (barcodeScannerDidScan:) could take an NSArray argument, rather than a single NSString. Internally, captureOutput:didOutputMetadataObjects:fromConnection: would then just need a single forin loop to check that the symbol matches the requested symbols, and use this loop to build an array. After the array is built, send it to the delegate.

• The return; can be removed from the nested forin loops. The result is the delegate method will be called once for each barcode that was scanned.

StackExchange Code Review Q#42252, answer score: 4