Count Time Spent across multiple view controllers ios - ios

Question

I have an iOS App that provides test for users with time limit.
The test will span across multiple view controllers, where these view controllers may re-open during the test flow. I think of the following flow:
In AppDelegate.h, add a NSTimer and time spent in float:
#property (strong, nonatomic) NSTimer *timer;
#property (nonatomic) float timeSpent;
- (void)startTimer;
- (void)stopTimer;
Without forgetting #synthesize the above, make a start & stop timer function in AppDelegate.m:
- (void)startTimer {
self.timer = [NSTimer scheduledTimerWithTimeInterval: 0.1f target: self
selector: #selector(updateTime) userInfo: nil repeats: YES];
}
- (void)stopTimer {
[self.timer invalidate];
}
In the periodically-called updateTime function, increment the value of timeSpent by 1.
Last, in each View Controller, obtain the timeSpent value and format it with the format I want, such as "01min 56s", or "01:56".
Is there a simpler way to do so?
Note:
No Internet connection available, and the test will last for around 10 minutes only; thus using Google Analytics is an overkill & not applicable in this case

Answer 1

You are correct that you need one NSTimer and variable to track the global time and..
What you are proposing, using the app delegate as a glorified singleton will work..
But please don't, this is not very good practice. This blog post has a nice brief description on why, in my opinion at least.
http://www.cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html
Personally if it was me I would probably just use a dependency injection model and pass the NSTimer between the viewControllers. http://www.objc.io/issue-15/dependency-injection.html
In short, app delegate is probably the easiest and quickest way. But I would advise something a little more scalable if it is going to be anything other than a trivial app.
Hope this was useful :)
*Edit Sample code for singleton.
This should go at the top of singleton class to initialise it.
#interface
#property (nonatomic, strong) NSTimer *myTimer;
#end
#implementation MySingletonClass
+ (instancetype)shared
{
static MySingletonClass *_shared = nil;
static dispatch_once_t oncePredicate;
dispatch_once(&oncePredicate, ^{
_shared = [[self alloc] init];
// any other initialisation you need
});
return _shared;
}
- (void)startTimer {
self.myTimer = [NSTimer scheduledTimerWithTimeInterval: 0.1f target: self
selector: #selector(updateTime) userInfo: nil repeats: YES];
}
- (void)stopTimer {
[self.myTimer invalidate];
}
then you can access it from any other classes in your program like this
#import "MySingletonClass.h"
//some method
- (void)myMethod
{
CGFloat currentTime = [MySingletonClass shared].globalTimeProperty;
// do something with the time
}
-(void)startTimer
{
[[MySingletonClass shared] startTimer];
}
-(void)updateTime
{
// do your update stuff here
}
Singleton header
#interface
#property (nonatomic, assign) CGFloat globalTimeProperty;
+ (instancetype)shared;
- (void)startTimer;
- (void)stopTimer;
#end
I may have missed some stuff but it should be enough to get you going.