Can't access object's properties after encoding it (crashes) - ios

Question

I have a custom class oject that I want to save using NSUserDefaults, this is how I saving it:
Shift.m
-(void)encodeWithCoder:(NSCoder*)encoder
{
[encoder encodeObject:self.date forKey:#"date"];
[encoder encodeObject:self.startTime forKey:#"startTime"];
[encoder encodeObject:self.endTime forKey:#"endTime"];
}
- (id)initWithCoder:(NSCoder *)decoder {
if(self = [super init]) {
self.date = [decoder decodeObjectForKey:#"date"];
self.startTime = [decoder decodeObjectForKey:#"startTime"];
self.endTime = [decoder decodeObjectForKey:#"endTime"];
}
return self;
}
MyTableViewController.m:
-(void)saveCustomObject:(id)object forKey:(NSString*)key
{
NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:object];
[[NSUserDefaults standardUserDefaults] setObject:encodedObject forKey:key];
}
-(NSArray*)getCustomObjectForKey:(NSString*)key
{
NSData *encodedObject = [[NSUserDefaults standardUserDefaults] objectForKey:key];
NSArray *shifts=[NSArray arrayWithObjects:[NSKeyedUnarchiver unarchiveObjectWithData:encodedObject], nil];
return shifts;
}
It seems it works fine when debugging, but when I try to access one of the object properties, for example on tableView: cellForRowAtIndexPath: like that:
Shift *currentShift=[self.shifts objectForIndex:indexPath.row];
NSLog(#"%#",currentShift.startTime.description);
It crashes with that crash message:
2016-03-19 09:04:05.913 MyApp[9654:4249448] -[__NSArrayM startTime]: unrecognized selector sent to instance 0x7ff81b449c10
2016-03-19 09:04:05.924 MyApp[9654:4249448] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM startTime]: unrecognized selector sent to instance 0x7ff81b449c10'
*** First throw call stack:
(
0 CoreFoundation 0x000000010e3e9e65 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x000000010de62deb objc_exception_throw + 48
2 CoreFoundation 0x000000010e3f248d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000010e33f90a ___forwarding___ + 970
4 CoreFoundation 0x000000010e33f4b8 _CF_forwarding_prep_0 + 120
5 Mehuyavut count 0x000000010d95a8e8 -[shiftsTableViewViewController tableView:cellForRowAtIndexPath:] + 600
6 UIKit 0x000000010e8efe43 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 766
7 UIKit 0x000000010e8eff7b -[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 74
8 UIKit 0x000000010e8c4a39 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2996
9 UIKit 0x000000010e8f901c -[UITableView _performWithCachedTraitCollection:] + 92
10 UIKit 0x000000010e8dfedc -[UITableView layoutSubviews] + 224
11 UIKit 0x000000010e84d4a3 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 703
12 QuartzCore 0x000000011231959a -[CALayer layoutSublayers] + 146
13 QuartzCore 0x000000011230de70 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366
14 QuartzCore 0x000000011230dcee _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
15 QuartzCore 0x0000000112302475 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 277
16 QuartzCore 0x000000011232fc0a _ZN2CA11Transaction6commitEv + 486
17 QuartzCore 0x000000011233037c _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 92
18 CoreFoundation 0x000000010e315367 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
19 CoreFoundation 0x000000010e3152d7 __CFRunLoopDoObservers + 391
20 CoreFoundation 0x000000010e30af2b __CFRunLoopRun + 1147
21 CoreFoundation 0x000000010e30a828 CFRunLoopRunSpecific + 488
22 GraphicsServices 0x0000000111ba6ad2 GSEventRunModal + 161
23 UIKit 0x000000010e796610 UIApplicationMain + 171
24 Mehuyavut count 0x000000010d95b5af main + 111
25 libdyld.dylib 0x0000000110b2592d start + 1
26 ??? 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Any one knows why?
Thank you!

Answer 1

It seems like you want Shift *currentShift=[self.shifts objectForIndex:indexPath.row] to give you 1 Shift object, but what it really does is returning a NSArray. You basically call a startTime method in NSArray, and since it doesn't exist, your program fails.
It seems like NSLog(#"%#",currentShift.startTime.description) is the line doing that. Confirm by commenting out the NSLog. It shouldn't give you a crash.
If this hypothesis is fine, check if [currentShift isKindOfClass:[NSArray class]] is true.
If it is, a bug you have in this line:
NSArray *shifts=[NSArray arrayWithObjects:[NSKeyedUnarchiver unarchiveObjectWithData:encodedObject], nil];
You also don't really show how your - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section looks like. You must return proper number of entries there.

Answer 2

You're making self.shifts be an NSArray, but you use objectForKey, which is available for dictionaries. It's not available for arrays. I think you wanted objectAtIndex instead.