Question

I want to write a dictionary that has custom objects all of the same type into the cache directory. I don’t know what is wrong but nothing is written. writeToFile returns false. This was working when I needed to save just a single user instance but now I need a dictionary. The dictionary keys are strings. The strange thing is initWithCoder and encodeWithCoder aren’t called at all.

I get the cache folder like this

NSString * NSCacheDirectory()
{
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); 
  NSString *cacheDirectory = [paths objectAtIndex:0]; 
#ifdef DEBUG
  NSString *regi = [NSHomeDirectory() stringByAppendingPathComponent: @"/Library/Caches/"];
#endif
  return  cacheDirectory;
  //return [NSHomeDirectory() stringByAppendingPathComponent: @"/Library/Caches/"];
}

I save a dictionary like this:

+(void) saveSharedUsers {
  NSString *cacheDir = NSCacheDirectory();
  NSFileManager *fm = [[NSFileManager alloc] init];
  Boolean success = true;
  NSError *error = nil;

  if (![fm fileExistsAtPath: cacheDir ])
    success = [fm createDirectoryAtPath: cacheDir withIntermediateDirectories: true attributes: nil error: &error];
  success = [[User sharedUsers] writeToFile: [NSCacheDirectory() stringByAppendingPathComponent: USER_FILE] atomically: true];
  [fm release];
}

User object:

@interface User : NSObject <NSCoding> {
  NSString    *email;
  NSInteger   userId;
  NSString    *name;
  NSString    *facebookId;
}

@property(nonatomic, copy)   NSString    *email;
@property(nonatomic, assign) NSInteger   userId;
@property(nonatomic, copy)   NSString    *name;
@property(nonatomic, copy)   NSString    *facebookId;
...
@end

@implementation User
...
@synthesize email,userId,name, facebookId;
- (void) encodeWithCoder:(NSCoder *)aCoder
{
  [aCoder encodeObject: self.name forKey:@"name"];
  [aCoder encodeObject: self.email forKey:@"email"];
  [aCoder encodeObject: self.facebookId forKey:@"facebookId"];
  [aCoder encodeInteger: self.userId forKey: @"userId"];
}

- (id) initWithCoder:(NSCoder *)aDecoder
{
  self = [super init];
  if (self != nil)
  {
    self.name = [aDecoder decodeObjectForKey: @"name"];
    self.email = [aDecoder decodeObjectForKey: @"email"];
    self.facebookId = [aDecoder decodeObjectForKey: @"facebookId"];
    self.userId = [aDecoder decodeIntegerForKey: @"userId"];
  }
  return self;
}
...
@end

Answer 1

I’m assuming that -[User sharedUsers] is an instance of NSDictionary. Then you’ll be writing a plist file to that location, not the archived data.

You should try this:

NSData *archivedUsers = [NSKeyedArchiver archivedDataWithRootObject:[User sharedUsers]];
[archivedUsers writeToFile: [NSCacheDirectory() stringByAppendingPathComponent: USER_FILE] atomically: true];

That will archive the objects and write the archived data to disk.

Loading the data is the reverse operation:

NSDictionary *users = [NSKeyedUnarchiver unarchiveObjectWithData:archivedUsers];