I'm trying to store some custom class/data to a file in my iPhone/iPad app.
I have a Class RSHighscoreList
@interface RSHighscoreList : NSObject {
NSMutableArray *list;
}
which contains objects of RSHighscore in the list
@interface RSHighscore : NSObject {
NSString *playerName;
NSInteger points;
}
When I try to store all to file
- (void)writeDataStore {
RSDataStore *tmpStore = [[RSDataStore alloc] init];
_tmpStore.highscorelist = self.highscorelist.list;
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:tmpStore forKey:kDataKey];
[archiver finishEncoding];
[data writeToFile:[self dataFilePath] atomically:YES];
[archiver release];
[data release];
}
@interface RSDataStore : NSObject <NSCoding, NSCopying> {
NSMutableArray *highscorelist;
}
- (void)encodeWithCoder:(NSCoder *)encoder {
[encoder encodeObject:highscorelist forKey:@"Highscorelist"];
}
The app will crash with an error message
-[RSHighscore encodeWithCoder:]: unrecognized selector sent to instance 0x573cc20 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[RSHighscore encodeWithCoder:]: unrecognized selector sent to instance 0x573cc20'
I wonder why the error tells about RSHighscore, even if that is 'wrapped'. Does anyone have a good idea?
RSDataStore
has an -encodeWithCoder:
method, but (according to the error message) RSHighscore
doesn't. You need to implement the NSCoding protocol for every class you're serializing.
@implementation RSHighscore
static NSString *const kPlayerName = @"PlayerName";
static NSString *const kPoints = @"Points";
-(id)initWithCoder:(NSCoder *)decoder {
if ((self=[super init])) {
playerName = [[decoder decodeObjectForKey:kPlayerName] retain];
points = [decoder decodeIntegerForKey:kPoints];
}
return self;
}
-(void)encodeWithCoder:(NSCoder *)encoder {
[encoder encodeObject:playerName forKey:kPlayerName];
[encoder encodeInt:points forKey:kPoints];
}
...
If the base class of RSHighscore
is ever changed to something other than NSObject
, the -initWithCoder:
method might need to be changed to call [super initWithCoder:decoder]
rather than [super init]
. Alternatively, add <NSCoding>
to NSObject and change RSHighscore
's -initWithCoder:
now.
@interface NSObject (NSCoding)
-(id)initWithCoder:(NSCoder*)decoder;
-(void)encodeWithCoder:(NSCoder*)encoder;
@end
@implementation NSObject (NSCoding)
-(id)initWithCoder:(NSCoder*)decoder {
return [self init];
}
-(void)encodeWithCoder:(NSCoder*)encoder {}
@end
@implementation RSHighscore
-(id)initWithCoder:(NSCoder *)decoder {
if ((self=[super initWithCoder:decoder])) {
playerName = [[decoder decodeObjectForKey:kPlayerName] retain];
points = [decoder decodeIntegerForKey:kPoints];
}
return self;
}
...