ios - uidatepicker [__NSDate 日期] : unrecognized selector sent to instance

Question

我正在使用 uidatepicker 并在尝试从日期选择器获取日期时抛出异常。

.h文件:

#import <UIKit/UIKit.h>

@protocol TimeDelegate <NSObject>
- (void)returnTime:(NSDate *)item;

@end

@interface TimeController : UIViewController <UIPickerViewDelegate>
{
    UIDatePicker *timePicker;
}
@property (nonatomic, weak) id <TimeDelegate> delegate;
@property (nonatomic, retain) IBOutlet UIDatePicker *timePicker;
@property (nonatomic, retain) NSDate *activityTime;
@end

.m文件

#import "TimeController.h"



@implementation TimeController

@synthesize timePicker;

- (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.
    self.timePicker  = [NSDate date];

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
-(void) viewDidDisappear:(BOOL)animated
{
    NSLog(@"%@", self.activityTime);
    //NSDate *itemToPassBack = [self.timePicker date];
    [self.delegate returnTime:self.activityTime];
}


- (IBAction)SelectTime:(id)sender {
    self.activityTime = [timePicker date];
}

@end

当我单击选择或导航返回时发生错误。最初我认为日期选择器在 viewdiddisappear 期间不可用并且抛出异常。选择按钮的行为也相同，这让我怀疑是否还有其他问题。

Answer 1

在 viewDidLoad 中，这一行:

self.timePicker  = [NSDate date];

将 NSDate 对象分配给 timePicker(声明为 UIDatePicker 对象)。

稍后，代码尝试通过调用 date 实例方法获取日期选择器的当前日期值，并且(幸运的是)失败并返回 unrecognized selector 因为 NSDate(timePicker 现在指向的)没有这样的实例方法。

你在 viewDidLoad 中真正想做的是:

self.timePicker.date  = [NSDate date];

在 timePicker 内设置 date 属性。