NSUserDefaults not saving mutable array of objects - ios

Question

I'm having trouble making a mutable array of objects persistent using NSUserDefaults. I've been trying different code for days and just can't get it right. I've read everything I can find on the subject, including all the postings in StackOverflow. I know I'm close, but I would really appreciate someone pointing out what I'm doing wrong. I know arr in the following code winds up with a count of zero, and that's where I hit a roadblock. I haven't gotten past that point. I'll bet someone will laugh and point our my silly error within 2 minutes of reading my post.
Here's the relevant code, including the log:
Contacts.h:
#interface Contacts : NSObject // <NSCoding>
{
NSMutableArray *arr; // 8/21/13
}
Contacts.m
- (void)encodeWithCoder:(NSCoder *)aCoder
{
NSLog(#"In encodeWithCoder");
NSLog(#"In encodeWithCoder. arr's count is: %i", [arr count]);
{
for (int i = 0; i <[arr count]; i++)
{
NSLog(#"In encodeWithCoder %#", [arr objectAtIndex:i]);
NSLog(#"class %#", [arr class]);
}
[aCoder encodeObject:arr forKey:#"allContacts"];
}
}
- (id) initWithCoder:(NSCoder *)aDecoder
{
NSLog(#"In initWithCoder");
arr = [aDecoder decodeObjectForKey:#"allContacts"];
return self;
}
// The following two methods might not even be needed. I copied them from some examples.
- (NSData *)dataOftype:(NSString *)typeName error:(NSError **)outError
{
return nil;
}
- (BOOL)readFromData:(NSData *)data oftype:(NSString *)typeName error: (NSError **)outError
{
arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];
NSLog(#"allContacts is ->%#", [arr mutableCopy]);
return YES;
}
ContactStore.h
#interface ContactsStore : NSObject <NSCoding>
{
NSMutableArray *arr; // 8/21/13
NSMutableArray *allContacts;
}
ContactStore.m
- (void)fetchContactsIfNecessary
{
NSLog(#"in ContactsStore.m - fetchContactsIfNecessary #1");
if (!allContacts)
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:#"allContacts"];
allContacts = [[NSMutableArray alloc]initWithArray:[NSKeyedUnarchiver unarchiveObjectWithData:data]];
for (int i = 0; i <[allContacts count]; i++)
{
NSLog(#"In FetchContactsIfNecessary- Gettingfrom NSUserDefaults %#", [allContacts objectAtIndex:i]);
NSLog(#"In FetchContactsIfNecessary- Gettingfrom NSUserDefaults - class %#", [allContacts class]);
}
}
// If we didn't find one in NSUserDefaults, then create a new one.
if (!allContacts)
{
allContacts = [[NSMutableArray alloc] init];
NSLog(#"In FetchContactsIfNecessary-We just allocated allContacts");
}
NSLog(#"in ContactsStore.m - Leaving fetchContactsIfNecessary2");
}
- (BOOL)saveChanges
{
for (int i = 0; i <[allContacts count]; i++)
{
NSLog(#"In saveChanges %#", [allContacts objectAtIndex:i]);
NSLog(#"In saveChanges class %#", [allContacts class]);
}
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
arr = allContacts; // 8/21/13
NSLog(#"In saveChanges. arr's count is: %i", [arr count]);
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:arr];
[defaults setObject:data forKey:#"allContacts"];
[[NSUserDefaults standardUserDefaults] synchronize];
NSLog(#"We just synchronized allContacts - I think");
return 1;
}
Log
2013-08-22 14:13:50.764 ImOK[16979:907] In saveChanges Scott Stringer, [phone]
2013-08-22 14:13:50.772 ImOK[16979:907] In saveChanges class __NSArrayM
2013-08-22 14:13:50.775 ImOK[16979:907] In saveChanges Sheldon Silver, [phone]
2013-08-22 14:13:50.781 ImOK[16979:907] In saveChanges class __NSArrayM
2013-08-22 14:13:50.793 ImOK[16979:907] In saveChanges. arr's count is: 2
2013-08-22 14:13:50.795 ImOK[16979:907] In encodeWithCoder
2013-08-22 14:13:50.796 ImOK[16979:907] In encodeWithCoder. arr's count is: 0
2013-08-22 14:13:50.798 ImOK[16979:907] In encodeWithCoder
2013-08-22 14:13:50.799 ImOK[16979:907] In encodeWithCoder. arr's count is: 0
2013-08-22 14:13:50.805 ImOK[16979:907] We just synchronized allContacts - I think
The names and phone numbers display correctly after the app returns from the background, but I get just four nulls after relaunching the app. I expected that because arr's count is zero in the method encodeWithCoder, but I can't figure out how to resolve this issue.

Answer 1

Your are only encoding and decoding your object. You don't store it yet. To store it you need a function like this:
- (BOOL)storeBrandOnDevice
{
NSString *path = [self itemArchivePath];
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:self forKey:#"Contacts"];
[archiver finishEncoding];
BOOL dataSaveSuccess = [data writeToFile:path atomically:YES];
return dataSaveSuccess;
}
to get them from the store something like this:
- (void) getBrandFromStorage
{
NSString *path = [self itemArchivePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
NSData *data = [[NSMutableData alloc] initWithContentsOfFile:path];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Contacts* storedContacts = [unarchiver decodeObjectForKey:#"Contacts"];
[unarchiver finishDecoding];
}
}
and here is your missing function:
- (NSString*)itemArchivePath
{
#try {
NSArray* documentDirectories = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentDirectory = [documentDirectories objectAtIndex:0];
return [documentDirectory stringByAppendingPathComponent:#"items.archive"];
}
#catch (NSException *exception) {
return nil;
}
}
It may not be perfect, but that's the general concept.
For more information about NSCoding, follow Ray Wenderlich's tutorial