Trying to make this work... (Xcode for mac NOT iPhone) - ArrayController - objective-c

Question

I'm writing a stopwatch application for mac, and am currently working on the 'laps' feature. I am putting the laps into a Table View for better organization. I'm using an Array Controller to put things into the table.
Basically, what I'm trying to do is this:
[arrayController addObject: [NSMutableDictionary dictionaryWithObjectsAndKeys:#"Lap 1",
#"lapNumber", nil]];
That works fine and dandy, but I'd like to be able to control that number next to lap using an integer representing the number of laps, called numLaps. Thus, my code would be:
[arrayController addObject: [NSMutableDictionary dictionaryWithObjectsAndKeys:#"Lap %i",
numLaps, #"lapNumber", nil]];
However, as that is more than two commas before the nil, I think the program is getting screwed up. I am getting the following thrown in the console, though I don't exactly understand what it means / how to fix it:
2013-09-03 16:52:31.515 Popup[3242:303] +[NSMutableDictionary dictionaryWithObjectsAndKeys:]: second object of each pair must be non-nil. Or, did you forget to nil-terminate your parameter list?
2013-09-03 16:52:31.519 Popup[3242:303] (
0 CoreFoundation 0x00007fff9800a0a6 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff9920b3f0 objc_exception_throw + 43
2 CoreFoundation 0x00007fff97fe8e31 +[NSDictionary dictionaryWithObjectsAndKeys:] + 433
3 Popup 0x00000001000035a0 -[PanelController btnLapWasClicked:] + 192
4 AppKit 0x00007fff96082a59 -[NSApplication sendAction:to:from:] + 342
5 AppKit 0x00007fff960828b7 -[NSControl sendAction:to:] + 85
6 AppKit 0x00007fff960827eb -[NSCell _sendActionFrom:] + 138
7 AppKit 0x00007fff96080cd3 -[NSCell trackMouse:inRect:ofView:untilMouseUp:] + 1855
8 AppKit 0x00007fff96080521 -[NSButtonCell trackMouse:inRect:ofView:untilMouseUp:] + 504
9 AppKit 0x00007fff9607fc9c -[NSControl mouseDown:] + 820
10 AppKit 0x00007fff9607760e -[NSWindow sendEvent:] + 6853
11 AppKit 0x00007fff96073744 -[NSApplication sendEvent:] + 5761
12 AppKit 0x00007fff95f892fa -[NSApplication run] + 636
13 AppKit 0x00007fff95f2dcb6 NSApplicationMain + 869
14 Popup 0x0000000100001652 main + 34
15 Popup 0x0000000100001624 start + 52
)
Any ideas how to implement what I'm trying to do in another fashion that won't confuse the program?
Thanks.

Answer 1

You should use the modern obj-c notation. That enables you to create dictionaries and arrays in a more natural way.
NSDictionary *dic = #{#"Laps ": #(numLaps), #"someotherkey":#"anditswalue"};
In the code you show the keys and values are not in pairs. You must always insert pairs. (For detailed reference see the NSDictionary documentation.)
NSString *key = #"laps";
NSString *value = [NSStringWithFormat:#"Lap %i", numLaps];
[arrayController addObject: [NSMutableDictionary dictionaryWithObjectsAndKeys:
value, key, nil]];
Also, you need to think over what you want to store in the dictionary. The keys and values are not apparent in your example.