Recursive archiving of classes in Objective C

Question

Let's say that I define a ClassA , that implements NSCoding protocol (this class contains several variables such as NSString, NSArray etc.). I also create a ClassB, that has a variable of type ClassA in it. Something like this:

 @interface ClassB: NSObject <NSCoding>
 {
     NSString *str;
     NSDate *date;
     int x;
     ClassA *sc;
 } 

In my program, I'd like to archive a variable of type ClassB. Is it possible to recursiverly archive custom objects? If so, how?

Thanks!

Answer 1

You need to implement the NSCoding interface for your ClassB:

- (id)initWithCoder:(NSCoder *)decoder
{
    self = [super initWithCoder:decoder];
    if (self)
    {
        str = [[decoder decodeObjectForKey:@"MyStr"] retain];
        date = [[decoder decodeObjectForKey:@"MyDate"] retain];
        x = [decoder decodeIntegerForKey:@"MyX"];
        sc = [decoder decodeObjectForKey:@"MyClassA"];
    }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)encoder
{
    [super encodeWithCoder:encoder];
    [encoder encodeObject:str forKey:@"MyStr"];
    [encoder encodeObject:date forKey:@"MyDate"];
    [encoder encodeInteger:x forKey:@"MyX"];
    [encoder encodeObject:sc forKey:@"MyClassA"];
}

ClassA must implement the NSCoding protocol as well.