ios - How to serialize a NSDictionary/NSArray/Property List (plist) which contains NSNull

Question

I want to store in a NSMutableDictionary some null values using NSNull and then serialize this data using a property list. Problem is NSNull is not allowed and I get "Property list is in invalid format" error. Is there a workaround for this? Seems very surprising they didn't put NSNull on the list of valid plist objects.

Answer 1

I convert NSArray or NSDictionary to NSData before serializing. Following is a category on nsarray for serializing and deserializing. This comfortableby handles some data being nsnull

@implementation NSArray(Plist)

-(BOOL)writeToPlistFile:(NSString*)filename{
    NSData * data = [NSKeyedArchiver archivedDataWithRootObject:self];
    NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString * documentsDirectory = [paths objectAtIndex:0];
    NSString * path = [documentsDirectory stringByAppendingPathComponent:filename];
    BOOL didWriteSuccessfull = [data writeToFile:path atomically:YES];
    return didWriteSuccessfull;
}

+(NSArray*)readFromPlistFile:(NSString*)filename{
    NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString * documentsDirectory = [paths objectAtIndex:0];
    NSString * path = [documentsDirectory stringByAppendingPathComponent:filename];
    NSData * data = [NSData dataWithContentsOfFile:path];
    return  [NSKeyedUnarchiver unarchiveObjectWithData:data];
}