BKTracker

BKTracker is a state tracking system to take snapshots of your application state for user defined 'events'. This was written to enhance the analytic data that I gather for my iphone applications. The primary design goals were to:

• Add time based information like:

  • Amount of time in a state
  • Amount of time since last event

• Easily Collect application state

  • Grab application and data-set information every time an event occurs
  • Application state is independent of what event occurs
  • Better to have more data than less

The code is a simple singleton that allows you to name states and add KeyPath to Name variables. IE:

- (void) addState:(NSString*)stateName;
- (void) addVariable:(NSString*)variableName keypath:(NSString*)keypath toState:(NSString*)stateName;

Then whenever an event occurs, it evaluates the keypaths on the instance object giving all sorts of data points to correlate with the event.

This is wrapped up in a UIViewController Category, to give you an API like this:

 - (void) viewDidLoad {
      self.trackerState = @"ProjectView";
      [self trackKeyPath:@"lapse.shots.@count" as:@"Shot Count"];
      [self trackKeyPath:@"lapse.reminders.@count" as:@"Reminder Count"];
      [self trackKeyPath:@"swapCount" as:@"Swap Count"];
 }

- (void) viewDidAppear:(BOOL)animated {
    [self enterTrackerState];
}

- (void) viewDidDisappear:(BOOL)animated {
    [self exitTrackerState];
}

- (IBAction) buttonClicked {
    [self trackEvent:@"TrackMe"
}

Then when buttonClicked is called, my delegate gets triggered and can send the dictionary to an analytic service like mixpanel or localytics.

delegateEvent:TrackMe attributes:{
    "Project Count" = 2;
    "Reminder Count" = 0;
    "Swap Count" = 4;
}

One design decision that I would like feedback on is making the UIViewController enhancements a category and not a subclass. I did this because I want it to be easy to plug into apps, and I do not like using libraries that force me to use their UIViewController subclass. What if I have my own generic subclass and already use this other cool project that has it's own UIViewController subclass?!

Along that line, There are routines in there to swizzle viewDidAppear and viewDidDisappear rather than writing that long, lengthy, wordy [self enterTrackerState] command. The options as I see them are below:

• 1 Be verbose juggling state
• 2 Subclass UIViewController
• 3 Extend and Swizzle UIViewController
• 4 Have UIKit emit NSNotifications on view[Did|Will][Disa|A]ppear] events.

Ideally 4 would occur, but it doesn't. So I'm stuck with 1.