Question

I am stumped here. I am just trying to save an NSArray populated with either NSNumbers or NSStrings to NSUserDefaults. Weird thing is it works if I save it right before I read it – but if I don’t save it and read it (after it has been saved on a prior launch) it is nil. It is like the defaults are being wiped out each time I hit Run (Command-R) in XCode.

NSArray *arrayToSave = [NSArray arrayWithObjects: [NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], nil];
[[NSUserDefaults standardUserDefaults] setObject:arrayToSave forKey:@"TestKey"];  //if I comment this line arrayRead will be nil even after I had saved it with this line on a prior run

Read it:

NSArray *arrayRead = [[NSUserDefaults standardUserDefaults] objectForKey: @"TestKey"];
NSLog(@"arrayRead: %@", arrayRead);

Answer 1

You should call synchronize after writing to user defaults:

// Write
NSArray *arrayToSave = [NSArray arrayWithObjects: [NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], nil];
[[NSUserDefaults standardUserDefaults] setObject:arrayToSave forKey:@"TestKey"];
[[NSUserDefaults standardUserDefaults] synchronize];

// Read
NSArray *arrayRead = [[NSUserDefaults standardUserDefaults] objectForKey:@"TestKey"]; // or arrayForKey
NSLog(@"arrayRead: %@", arrayRead);