ios storing custom objects - iphone

Question

How can I store NSMutableArray of custom objects?
I have this code for loading and saving files:
- (NSMutableArray *)loadDataFromFile:(NSString *)fileName {
NSError *error;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docDir = [paths objectAtIndex:0];
NSString *path = [docDir stringByAppendingPathComponent:fileName];
NSFileManager *fileMgr = [NSFileManager defaultManager];
if (![fileMgr fileExistsAtPath:path]) {
NSArray *fileArray = [fileName componentsSeparatedByString:#"."];
NSString *name = [fileArray objectAtIndex:0];
NSString *ext = [fileArray objectAtIndex:1];
NSString *bundle = [[NSBundle mainBundle] pathForResource:name ofType:ext];
[fileMgr copyItemAtPath:bundle toPath:path error:&error];
}
NSMutableArray *data = [[NSMutableArray alloc] initWithContentsOfFile:path];
return data;
}
- (void)saveData:(NSMutableArray *)arrayData toFile:(NSString *)filename forKey:(NSString *)key {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docDir = [paths objectAtIndex:0];
NSString *path = [docDir stringByAppendingPathComponent:filename];
[arrayData writeToFile: path atomically:YES];
NSLog(#"%#", arrayData);
}
But when I used data.plist as filename, it didn't work because NSLog(#"%#", arrayData); returns list custom object adresses:
"AreaTableRecord: 0x76a7ef0"
This custom object is inserted to array using this code:
AreaTableRecord *area=[[AreaTableRecord alloc] init];
area.title=title;
area.lastScore=0;
area.vocabulary=[[NSMutableArray alloc] init];
[self.areas addObject:area];
How could I store NSMutableArray self.areas that contains custom objects AreaTableRecord?
and
What file format shloud I use to store this data? (it seems to me that plist is not working in this case)

Answer 1

You are only able to store primitive data types in NSDefaults or a plist. In order to work around this you can either choose to store your information in a database....or encode your objects as byte streams and then save them into a file.
Take a look at this thread. It details how to go about encoding your objects.
Basically you need to add these methods to your custom class:
- (void)encodeWithCoder:(NSCoder *)encoder
{
//Encode properties, other class variables, etc
[encoder encodeObject:self.question forKey:#\"question\"];
[encoder encodeObject:self.categoryName forKey:#\"category\"];
[encoder encodeObject:self.subCategoryName forKey:#\"subcategory\"];
}
- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if( self != nil )
{
//decode properties, other class vars
self.question = [decoder decodeObjectForKey:#\"question\"];
self.categoryName = [decoder decodeObjectForKey:#\"category\"];
self.subCategoryName = [decoder decodeObjectForKey:#\"subcategory\"];
}
return self;
}
And then in order to use them you make calls as such:
For setting:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *myEncodedObject = [NSKeyedArchiver archivedDataWithRootObject:obj];
[defaults setObject:myEncodedObject forKey:#\"myEncodedObjectKey\"];
For retrieving:
NSUserDefaults defaults = [NSUserDefaults standardUserDefaults];
NSData *myEncodedObject = [defaults objectForKey: key];
MyCustomObject* obj = (MyCustomObject*)[NSKeyedUnarchiver unarchiveObjectWithData: myEncodedObject];