UPC-A support

[yporubov]

Thank you so much for the barcode generator.

From "AVMetadataObjectTypeEAN13Code" description: AVMetadataMachineReadableCodeObject instances generated from EAN-13 (including UPC-A) codes return this identifier as the type.

The barcode does have length 12 digits, like 123456789012. EAN-13 barcode does have 13 digits
isContentsValid method returns NO because contents.length == self.length is not TRUE. (12 != 13)
As workaround I added one zero before barcode (0123456789012) and it works for me.
[CodeGen genCodeWithContents:@"0123456789012" machineReadableCodeObjectType:objectType]

But could you please add zero inside API ?

[Reinoal]

首先感谢你的分享，我使用的版本是0.1.4
在扫描二维码的结束，controller被退出之后alert会被多次调用并显示。怎么解决这个问题： if (barcodeObjects.count > 0) {
[barcodeObjects enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
dispatch_async(dispatch_get_main_queue(), ^{
AVMetadataMachineReadableCodeObject *code = obj;
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Barcode found"
message:code.stringValue
delegate:self
cancelButtonTitle:@"OK"
otherButtonTitles:nil];
dispatch_async(dispatch_get_main_queue(), ^{
[scanner dismissViewControllerAnimated:true completion:nil];
[alert show];
});