Igy kell megkeresni az NSDocumentDirectory-t

innen

Locating Directories as Paths

The following example illustrates how you can use the NSSearchPathForDirectoriesInDomains function to find the current user’s Documents directory:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

if ([paths count] > 0) {

NSString *userDocumentsPath = [paths objectAtIndex:0];

// Implementation continues...

NSSearchPathForDirectoriesInDomains simply returns the path of the appropriate directory, it does not guarantee that the directory exists. If you want to perform operations such as writing to the directory, you may have to create it first.