Need some help on how to construct/use a delegate - ios

Question

I'm struggling with delegate creation and usage. Could someone help me understand what I'm doing wrong? According to all the examples I have read this is correct but my data is not being returned.
ViewController (Parent)
.h
#import <UIKit/UIKit.h>
#import "BarcodeViewController.h"
#interface ViewController: UIViewController <BarcodeViewDelegate> {
IBOutlet UILabel *bcode;
}
#end
.m
-(void)setbarcode:(NSString*)barcode
{
NSLog(#" data %#", barcode);
bcode.text = barcode;
}
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Make sure your segue name in storyboard is the same as this line
if ([[segue identifier] isEqualToString:#"scanbarcode"])
{
BarcodeViewController *cv = [segue destinationViewController];
cv.delegate = self;
}
}
The Barcode view controller (Child view)
.h
#protocol BarcodeViewDelegate <NSObject>
-(void)setbarcode:(NSString*)barcode;
#end
#interface BarcodeViewController : UIViewController
{
id<BarcodeViewDelegate> delegate;
}
#property(nonatomic,assign)id delegate;
#end
.m
#import "BarcodeViewController.h"
#import <AVFoundation/AVFoundation.h>
#interface BarcodeViewController () <AVCaptureMetadataOutputObjectsDelegate>
{
AVCaptureSession *_session;
AVCaptureDevice *_device;
AVCaptureDeviceInput *_input;
AVCaptureMetadataOutput *_output;
AVCaptureVideoPreviewLayer *_prevLayer;
UIView *_highlightView;
UIImageView *_imageOverlay;
}
#end
#implementation BarcodeViewController
- (void)viewDidLoad
{
[super viewDidLoad];
/*
* setup scanner view
*/
_highlightView = [[UIView alloc] init];
_highlightView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin|UIViewAutoresizingFlexibleBottomMargin;
_highlightView.layer.borderColor = [UIColor greenColor].CGColor;
_highlightView.layer.borderWidth = 3;
[self.view addSubview:_highlightView];
/*
* setup a overlay guide
*/
_imageOverlay = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"camera_overlay"]];
[self.view addSubview:_imageOverlay];
_session = [[AVCaptureSession alloc] init];
_device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
NSError *error = nil;
_input = [AVCaptureDeviceInput deviceInputWithDevice:_device error:&error];
if (_input) {
[_session addInput:_input];
} else {
NSLog(#"Error: %#", error);
}
_output = [[AVCaptureMetadataOutput alloc] init];
[_output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
[_session addOutput:_output];
_output.metadataObjectTypes = [_output availableMetadataObjectTypes];
_prevLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
_prevLayer.frame = self.view.bounds;
_prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.view.layer addSublayer:_prevLayer];
[_session startRunning];
[self.view bringSubviewToFront:_highlightView];
[self.view bringSubviewToFront:_imageOverlay];
}
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
CGRect highlightViewRect = CGRectZero;
AVMetadataMachineReadableCodeObject *barCodeObject;
NSString *detectionString = nil;
NSArray *barCodeTypes = #[AVMetadataObjectTypeUPCECode, AVMetadataObjectTypeCode39Code, AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode93Code, AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypePDF417Code, AVMetadataObjectTypeQRCode, AVMetadataObjectTypeAztecCode];
/*
* keep looking around while we look for the barcode
*/
for (AVMetadataObject *metadata in metadataObjects) {
for (NSString *type in barCodeTypes) {
if ([metadata.type isEqualToString:type])
{
barCodeObject = (AVMetadataMachineReadableCodeObject *)[_prevLayer transformedMetadataObjectForMetadataObject:(AVMetadataMachineReadableCodeObject *)metadata];
//highlightViewRect = barCodeObject.bounds;
detectionString = [(AVMetadataMachineReadableCodeObject *)metadata stringValue];
break;
}
}
if (detectionString != nil)
{
/*
* Set the detected barcode so we can use it.
* - perform segway to another view
*/
//barcode = detectionString;
//NSLog(#" data %#", detectionString);
[delegate setbarcode: detectionString];
[self.navigationController popViewControllerAnimated:YES];
break;
}
//else
/*
* Just reset the barcode value for now
*/
//_barcode = false;
}
_highlightView.frame = highlightViewRect;
}
#end

Answer 1

Your problem is simple.
You define an instance variable and a property to hold the delegate:
{
id delegate;
}
#property(nonatomic,assign)id delegate;
You set the delegate via the property:
cv.delegate = self;
Then access it via the instance variable:
[delegate setbarcode: detectionString];
The property is backed by a different instance variable, automatically defined as _delegate, which you should not be accessing. You should always access via the property, as self.delegate. When calling your delegate ivar, it will be nil, so nothing is being sent back.
Remove the unnecessary instance variable declaration, type the property correctly (as id<BarcodeViewDelegate> rather than just id) and always access it via the property, and you'll be fine.