Question

I have a form with information first name and last name and some other information. I use a person class to store this information. on submit click I archiving it in a file person.txt using NSCoding implemented in person class. if I add multiple persons in the file person.txt, how can I get all the person objects stored in the file. decoding the person class just gives me the last added person.

Answer 1

If you want all of the person objects serialized, then you need the NSArray or whatever other collection class in which they are stored to be the root object for the NSKeyedArchiver. e.g.: (assumes ARC)

#import <Foundation/Foundation.h>

@interface Person:NSObject <NSCoding>
@property (nonatomic, copy) NSString *lastName;
@property (nonatomic, copy) NSString *firstName;
// etc.
@end

@implementation Person

@synthesize lastName = _lastName;
@synthesize firstName = _firstName;

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeObject:self.lastName forKey:@"ln"];
    [aCoder encodeObject:self.firstName forKey:@"fn"];
}

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if( !self ) { return nil; }

    _lastName = [aDecoder decodeObjectForKey:@"ln"];
    _firstName = [aDecoder decodeObjectForKey:@"fn"];

    return self;
}

@end

int main(int argc, char *argv[]) {
    NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];

    Person *me = [Person new];
    me.lastName = @"Kitten";
    me.firstName = @"Mittens";

    Person *you = [Person new];
    you.lastName = @"Youe";
    you.firstName = @"JoJo";

    NSArray *people = [NSArray arrayWithObjects:me,you,nil];
    NSData *serializedData = [NSKeyedArchiver archivedDataWithRootObject:people];

    //  write your serializedData to file, etc.

    [p release];
}

Why the .txt extension on your archive, though? It just binary data, right?