ios - Xcode:无效参数不令人满意

Question

在实现日期选择器后，我一直在 Xcode 中遇到一个非常令人沮丧的错误。调试器中的错误是:“由于未捕获的异常‘NSInternalInconsistencyException’而终止应用程序，原因:‘无效参数不满足:日期’

我已经检查我的代码几个小时了，但找不到问题所在。可能是因为我没有检查 nil，应用程序第一次安装和启动时没有日期，所以这可能导致崩溃。如果是，我如何检查此代码中的 nil？我在编程方面仍然很新，任何帮助将不胜感激。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

在使用它之前，你不检查日期是否为空，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];
}