Xcode：无效的参数不满意

Question

在实施日期选择器后，我在Xcode中遇到了一个非常令人沮丧的错误。调试器中的错误是：“因未捕获的异常而终止应用程序'NSInternalInconsistencyException'，原因：'无效的参数不满足：日期”

我几个小时以来一直在查看我的代码，但找不到问题。这可能是因为我没有检查nil，第一次安装和启动应用程序时没有日期，因此可能导致崩溃。如果是，我如何在此代码中检查nil？我在编程方面还很新，任何帮助都会非常感激。这是代码：

#import "DatePickerViewController.h"


@implementation DatePickerViewController
@synthesize datePicker;


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
    // Initialization code
    }
    return self;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning]; // Releases the view if it doesn't have a superview
    // Release anything that's not essential, such as cached data
}


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UILocalNotification *localNotif = [[UILocalNotification alloc] init];

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"mm'/'dd'/'yyyy"];

    NSDate *eventDate = [[NSUserDefaults standardUserDefaults] objectForKey:@"DatePickerViewController.selectedDate"];

    localNotif.fireDate = [eventDate dateByAddingTimeInterval:-13*60*60];
    localNotif.timeZone = [NSTimeZone defaultTimeZone];


    localNotif.alertBody = @"Tomorrow!";

    localNotif.alertAction = nil;

    localNotif.soundName = UILocalNotificationDefaultSoundName;
    localNotif.applicationIconBadgeNumber = 0;
    [[UIApplication sharedApplication]presentLocalNotificationNow:localNotif];    

    return YES;
}


- (void)viewDidLoad {
    NSDate *storedDate = [[NSUserDefaults standardUserDefaults] 
                  objectForKey:@"DatePickerViewController.selectedDate"];

    [self.datePicker setDate:storedDate animated:NO];
}

- (IBAction)dateChanged:(id)sender {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    NSDate *selectedDate = [self.datePicker date];

    [defaults setObject:selectedDate forKey:@"DatePickerViewController.selectedDate"];
}

Answer 1

在使用前，您不会检查日期是否为空，例如

(void)viewDidLoad {

    NSDate *storedDate = [[NSUserDefaults standardUserDefaults] 
                      objectForKey:@"DatePickerViewController.selectedDate"];

    // add this check and set
    if (storedDate == nil) {
        storedDate = [NSDate date];
    }
    // ---
    [self.datePicker setDate:storedDate animated:NO];
}

Answer 2

我发现一种Debug方式可以帮助您调试发生异常的位置，并可以帮助某些人进行异常调试。

1. 导航至断点

2. 单击添加按钮，然后选择异常断点

3. 添加断点并为Objective-C设置异常类型

4. 运行代码 它将停在发生崩溃的那一行！

希望有帮助〜