Xcode：无效的参数不满意

Question

I keep running into a pretty frustrating error in Xcode after implementing a date picker. The error in the debugger is: "Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid parameter not satisfying: date"

I've been going through my code for hours now, and can't find the issue. It may be because I'm not checking for nil, there is no date the first time the app installs and launches, so that may be causing the crash. If it is, how do I check for nil in this code? I'm still very new at programming, any help would be much appreciated. Here is the code:

#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

You don't check if date is null, before using it, in ex.

(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

I've find a Debug way may help you debug where is the exception occurred and may help someone to debug with exception.

1. navigate to breakpoint

2. Click the add button, and choose exception Breakpoint

3. Add breakpoint and make exception type to Objective-C

4. Run the code It will stop at the line which make crash happened!

Hope this help~