Question

我的cpViewController有一个按钮，模态分段到cpScanViewController。我希望cpScanViewController在完成成功扫描后通过字符串通知ViewController。在网上阅读了大量文章后，我相信代表团是最好的方式吗？

委托是否设置正确？
委托如何通知cpViewController？

cpScanViewController.h

#import <UIKit/UIKit.h>


@protocol ScanDelegate <NSObject>
-(void)receivedUPC:(NSString *)Scan;
@end

@interface cpScanViewController : UIViewController 
@property (nonatomic, weak) id <ScanDelegate> delegate;
@property (nonatomic, retain) NSString *UPC;
-(void)checkUPC;
@end

cpScanViewController.m

@interface cpScanViewController ()
{
  NSString *UPC;
}
@end

@implementation cpScanViewController
@synthesize delegate;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
    // Custom initialization
}
return self;
}

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
-(void)doSomeScanStuff
{
UPC = @"a string"
   // even tried
 [delegate receivedUPC:UPC];
}
-(void)checkUPC
{

}
@end

cpViewController.h

#import <UIKit/UIKit.h>
#import "cpScanViewController.h"

@interface cpViewController : UIViewController <ScanDelegate>

@end

cpViewController.m

@interface cpViewController ()
{
 cpScanViewController *cp;
}
@end

@implementation cpViewController

- (void)viewDidLoad
{
  // set delegate
cp = [[cpScanViewController alloc] init];
[cp setDelegate:self];

}
-(void)receivedUPC:(NSString *)Scan{
  // Nothing happening
NSLog(@"%@", Scan);    
NSLog(@"The %@", cp.UPC);
}
@end

Answer 1

因为您没有从receivedUPC课程中调用cpScanViewController方法。您需要在[_delegate receivedUPC:self]类中添加cpViewController，以便调用此委托方法。

Answer 2

我能够通过使用以下方法使其正常工作：

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    cpScanViewController *vd = (cpScanViewController *)[segue destinationViewController];
vd.delegate = self;
}

因为我在故事板中建立了连接，所以我没有意识到需要使用该方法。

代表不通知我的观点

2 个答案: