read and write using NSKeyedArchiver, ios - iphone

Question

Below is a class to read and write data using nsarchive
Data.m
-(id)init {
self = [super init];
if(self) {
arr = [[NSMutableArray alloc] init];
}
return self;
}
-(NSString *)getPath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentPath;
if ([paths count] > 0)
documentPath = [paths objectAtIndex:0];
NSString *draftDataPath = [documentPath stringByAppendingPathComponent:#"draftData.dat"];
return draftDataPath;
}
-(void)saveDataToDisk {
NSString *path = [self getPath];
[NSKeyedArchiver archiveRootObject:arr toFile:path];
}
-(void)loadDataFromDisk {
NSString *path = [self getPath];
self.arr = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
}
At later on, I am adding some objects into arr by doing
CustomerClass.m
- (void) viewDidLoad {
Data *data = [[Data alloc] init];
[data.arr addObject:myObject1]
[data.arr addObject:myObject2]
[data.arr addObject:myObject3]
[data saveDataToDisk];
}
At DisplayData.m, I want to check data.arr by
- (void) viewDidLoad {
Data *data = [[Data alloc] init];
[data loadDataFromDisk];
NSLog(#"length of array is %d",[data.arr count]);
}
On the console, I am getting
length of array is 1
I thought it should be 3 after all.
Please point out what I have just made a mistake in the middle of work if you have any clues about it.

Answer 1

So, I suspect that your "myObjects" are not NSCoding compliant. I just did this:
NSMutableArray *arr = [NSMutableArray arrayWithCapacity:3];
[arr addObject:#"Hello"];
[arr addObject:#" "];
[arr addObject:#"World"];
BOOL ret = [NSKeyedArchiver archiveRootObject:arr toFile:[self getPath]];
NSArray *arr2 = [NSKeyedUnarchiver unarchiveObjectWithFile:[self getPath]];
NSLog(#"count = %d", [arr2 count]);
And the results was "count = 3"

Answer 2

I feel like there's too much code here to do what you're looking for. I think all you need is:
[[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:dataClass] forKey:NSUserDefaultString];
[[NSUserDefaults standardUserDefaults] synchronize];
to save it.
And:
NSData *someData = [[NSUserDefaults standardUserDefaults] objectForKey:NSUserDefaultString];
if (settingsData != nil)
{
dataClass = [NSKeyedUnarchiver unarchiveObjectWithData:settingsData];
}
to retrieve it.