[Iphone] - Problem in saving file using NSCoding

Question

Hi everybody,

I've a problem with Iphone programming... I've a NSMutableArray containing object of type "MyClass". MyClass has some parameters, like NSNumber and NSString.

I've followed the Apple Tutorial about coding and decoding object using NSCoding, but when I try to decode the file I've stored, the NSMutableArray contain object of type "MyClass", but with wrong parameters.

I think i've done all I've to do (including protocol, including methods like initwithencode etc), but it's still not working...

Any suggestions?

Thanks a lot! And sorry for my English XD

Answer 1

Maybe seeing a simplified example will help. If not, we might be better able to assist with some code examples.

@interface MyObject : NSObject <NSCoding>
{
    NSUInteger MyObject_myInteger;
    MyEnum MyObject_myEnum;
    NSMutableArray *MyObject_myArray;
}

@end

@implementation MyObject

/** Implentation of the NSCoding protocol. */

-(void)encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeInt:MyObject_myInteger forKey:@"myInteger"];
    [encoder encodeInt:MyObject_myEnum forKey:@"myEnum"];
    [encoder encodeObject:MyObject_myArray forKey:@"myArray"];
}

-(id)initWithCoder:(NSCoder *)decoder
{
    // Init first.
    self = [self init];

    MyObject_myInteger = [decoder decodeIntForKey:@"myInteger"];
    MyObject_myEnum = [decoder decodeIntForKey:@"myEnum"];
    MyObject_myArray = [decoder decodeObjectForKey:@"myArray"];

[MyObject_myArray retain]; // Array is autoreleased, so we need to retain.

    return self;
}

@end

When your code archives an object of this class, make sure that you do it correctly. For example:

NSMutableData *stateInfo = [NSMutableData data];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:stateInfo];
[archiver autorelease];

// Encode our stateful objects.
[archiver encodeObject:MYAppDelegate_myObject forKey:@"myObject"];

// Wrap up the encoding process.  If you omit this, 
// then bad things will happen when you decode.
[archiver finishEncoding];

Good luck, and happy coding!

Answer 2

My class is something like this:

TorneoSingolo.h

@interface TorneoSingolo : NSObject <NSCoding> {
...
NSString *Descrizione;
...
}

- (void)encodeWithCoder:(NSCoder *)encoder;
- (id)initWithCoder:(NSCoder *)decoder;

@property(nonatomic, retain) NSString *Descrizione;

@end

TorneoSingolo.m

@implementation TorneoSingolo

@synthesize Descrizione;

- (void)encodeWithCoder:(NSCoder *)encoder

{
    [encoder encodeObject:self.NomeTorneo forKey:@"OBJ_NomeTorneo"];
    [encoder encodeObject:NomeSquadra forKey:@"OBJ_NomeSquadra"];
    [encoder encodeObject:self.Descrizione forKey:@"OBJ_Descrizione"];
    [encoder encodeInt: [self.NumPortieri intValue] forKey:@"OBJ_numportieri"];         
}

-(id)initWithCoder:(NSCoder *)decoder
{
    self = [self init];

    Descrizione = [decoder decodeObjectForKey:@"OBJ_Descrizione"];

    [Descrizione retain];

    return self;
}

The method that call the loading function works like this:

ElencoTornei2 = [[NSMutableArray alloc] init];

NSData *data;
NSKeyedUnarchiver *unarchiver;
NSString *archivePath = [rootPath stringByAppendingPathComponent:@"ElencoTornei.archive"];

if ([[NSFileManager defaultManager] fileExistsAtPath:archivePath]) {
    data = [NSData dataWithContentsOfFile:archivePath];
    unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];

    ElencoTornei2 = [unarchiver decodeObjectForKey:@"MyElencoTornei"];
    [unarchiver finishDecoding];
    [unarchiver release];

    [ElencoTornei2 retain];
}

I can't understand where i'm doing something wrong, like reinitialize an object...

please help me... =)

Answer 3

Here it is:

NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *archivePath = [rootPath stringByAppendingPathComponent:@"ElencoTornei.archive"];
BOOL result;

NSMutableData *stateInfo = [NSMutableData data];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:stateInfo];
[archiver autorelease];

[archiver encodeObject:ElencoTornei forKey:@"MyElencoTornei"];
[archiver finishEncoding];

if (![[NSFileManager defaultManager] fileExistsAtPath:archivePath]) {
    [[NSFileManager defaultManager] createFileAtPath:rootPath contents:stateInfo attributes:nil];
}
else {
    result = [stateInfo writeToFile:archivePath atomically:YES];
}

ElencoTornei (the object that has to be encoded) is a static NSMutableArray contained in the class that is containing this part of code... i didn't write any overload of the method encodewithcoder for this specific object because i hope it use the appropriated one...