writing data using NSKeyedArchiver - iphone

Question

I trying to learn how to save array of objects using NSKeyedArchiver and I coded a small application to do that and I logged to see if the array was saved but everytime I get 0 for array count and here is the code.
ViewController.h
#interface ViewController : UIViewController
{
IBOutlet UITextField *text;
IBOutlet UITextField *textName;
IBOutlet UITextField *textAge;
IBOutlet UILabel *name;
IBOutlet UILabel *age;
BOOL flag;
BOOL choice;
NSString *documentDirectory;
NSMutableArray *anArray;
Person *p;
NSData *data;
}
-(BOOL) dataFilePath;
-(IBAction)readPlist;
-(IBAction) writePlist;
#property (strong,nonatomic)IBOutlet UITextField *text;
#property (strong,nonatomic)IBOutlet UITextField *textName;
#property (strong,nonatomic)IBOutlet UITextField *textAge;
#property (strong,nonatomic)IBOutlet UILabel *name;
#property (strong,nonatomic)IBOutlet UILabel *age;
#property (strong,nonatomic)NSString *documentDirectory;
#property (strong,nonatomic)NSMutableArray *anArray;
#end
ViewController.m
#interface ViewController ()
#end
#implementation ViewController
#synthesize text,documentDirectory,textAge,textName,name,age,anArray;
- (void)viewDidLoad
{
[super viewDidLoad];
// checking if the file was created and show a message if its created or not.
if ([self dataFilePath]) {
NSLog(#"File Created !");
} else {
NSLog(#"File Not Created !");
}
NSLog(#"File location : %#",documentDirectory);
choice = YES;
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(BOOL) dataFilePath
{
NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
documentDirectory = [path objectAtIndex:0];
documentDirectory = [documentDirectory stringByAppendingPathComponent:#"Milmers­Data.dat"];
return TRUE;
}
- (IBAction)writePlist
{
p.name = textName.text;
p.age = [textAge.text intValue];
[anArray addObject:p];
for (int i=0; i<[anArray count]+1; i++) {
Person *pp = [[Person alloc]init];
pp=[anArray objectAtIndex:i];
NSLog(#"Name: %#",pp.name); // checking the names in pp object but getting null
}
data = [NSKeyedArchiver archivedDataWithRootObject:anArray];
[data writeToFile:documentDirectory options:NSDataWritingAtomic error:nil];
NSLog(#"Array length: %d",[anArray count]); //Always got array count zero.
}
-(IBAction)readPlist
{
NSString *filePath = documentDirectory;
NSMutableArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
NSLog(#"The array is: %#",array); // it shows that there is nothing in the array
}
#end
I wrote the class for writing .plist files originally but I knew later that I cant store objects in .plist file so I tried so that with archive, thats why the method name have plist in it.
Thank you in advance

Answer 1

Looks like you aren't ever creating an instance of p to add to the array. Try:
Person *p = [[Person alloc] init];
p.name = textName.text;
p.age = [textAge.text intValue];
[anArray addObject:p];
your index limit was also wrong in this loop
for (int i=0; i<[anArray count]; i++) {
NSLog(#"Name: %#", [[anArray objectAtIndex:i] name]);
}
you should really have been seeing a couple of different crashes...

Answer 2

Try adding this in viewDidLoad
[[NSFileManager defaultManager] createFileAtPath:documentDirectory contents:nil error:nil];
It looks like you never do this, and using archives to write to files only works if the file already exists (make sure you only do this once, otherwise every time that view is loaded the file will be emptied of all the data in it). And when you do this
if ([self dataFilePath])
It's pointless, because no matter what it always returns yes, whether the file exists or not.

Answer 3

Does your Person class implement NSCoding?
Specifically you need to implement something like the following in Person.m:
- (id)initWithCoder:(NSCoder *)decoder {
self = [super init];
if (!self) {
return nil;
}
self.name = [decoder decodeObjectForKey:#"name"];
self.age = [decoder decodeObjectForKey:#"age"];
return self;
}
- (void)encodeWithCoder:(NSCoder *)encoder {
[encoder encodeObject:self.name forKey:#"name"];
[encoder encodeObject:self.age forKey:#"age"];
}