iOS7在导航控制器推送视图设置中按协议向后传递数据

debugcn 发表于 Dev

内尔姆

我在代码中尝试了许多自定义委托示例，以将数据从视图B发送回父视图A。为什么会出现NULL？我应该缺少一些东西。请帮忙。如何在父视图中调用setupDate以接收（NSDate *）setAlarmDate？

父视图

#import "SetupViewController.h"

@interface ViewController : UIViewController <SetupViewControllerDelegate> {
NSTimer *timer;
}
@end

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if ([[segue identifier] isEqualToString:@"setupview"]) {
    NSLog(@"prepare for segue");
    SetupViewController *svc = [[SetupViewController alloc] init];
    svc.delegate = self;

-(void)setupDate:(NSDate *)setAlarmDate{
NSLog(@"Hey Hey");
NSLog(@"%@", setAlarmDate);
}
@end

查看B

@protocol SetupViewControllerDelegate <NSObject>
@required
-(void)setupDate:(NSDate *)setAlarmDate;
@end

@interface SetupViewController : UIViewController
@property (nonatomic, strong) id <SetupViewControllerDelegate> delegate;
//IB
@property (weak, nonatomic) IBOutlet UIDatePicker *pDatePicker;
@end

#import "SetupViewController.h"
#import "ViewController.h"
@implementation SetupViewController
-(void)viewWillDisappear:(BOOL)animated{
NSDate *date = [self.pDatePicker date];
[[self delegate] setupDate:date];
}
@end

乔纳森

您应该UIViewController使用segue的destinationViewController属性访问，而不是分配您自己的实例，这就是您的的原因alarmDate = NULL。

例如

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"setupview"])
    {
        NSLog(@"prepare for segue");
        SetupViewController *svc = [segue destinationViewController];
        svc.delegate = self;
    }
}

此外，正如@Neru所提到的，您的代表应被限定为软弱而不是强壮。这样做的原因是，如果未delegate = nil在dealloc方法中显式设置，则会导致一个保留周期。

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