Use core data entity in a countdown timer - loops

Question

I have 2 entities in core data to create countdown timers. Timer has an attribute called timerName and entity Blinds(changed from 'Times') has an attribute called duration.
Entities called
Timer <---->> Blind
and attributes called
timerName <---->> duration
with relationships called
blinds <---->>timer
I need to place the various durations into a countdown timer one at a time. When the first duration reaches 0 the next duration is fetched from core data and that is counted down to zero etc.
I am very new to Objective-C and core data but I know I need a loop and fetch request but don't know where to start. Any code examples would be appreciated. Thanks
EDIT
I have setup a fetchrequest in my model.m
- (NSFetchedResultsController *)frc_newTimer
{
if (_frc_newTimer) return _frc_newTimer;
// Otherwise, create a new frc, and set it as the property (and return it below)
_frc_newTimer = [_cdStack frcWithEntityNamed:#"Timer"
withPredicateFormat:nil
predicateObject:nil
sortDescriptors:#"timerName,YES"
andSectionNameKeyPath:nil];
return _frc_newTimer;
}
Then in my view controller.h
#import <UIKit/UIKit.h>
#import "Timer.h"
#import "Blind.h"
#interface BlindTimerViewController : UIViewController <NSFetchedResultsControllerDelegate>
{
IBOutlet UILabel *lblCountDown;
NSTimer *countdownTimer;
int secondsCount;
}
- (IBAction)StartTimer:(id)sender;
- (IBAction)ResetTimer:(id)sender;
#property (assign, nonatomic) NSInteger currentTimeIndex;
#property (nonatomic, strong) Model *model;
#property (nonatomic, strong) Timer *myTimer;
#end
then in view controller.m
#interface BlindTimerViewController ()
#end
#implementation BlindTimerViewController
#synthesize model = _model;
and
-(void) timerRun
{
secondsCount = secondsCount -1;
int minutes = secondsCount / 60;
int seconds = secondsCount - (minutes * 60);
NSString *timerOutput = [NSString stringWithFormat:#"%2d:%.2d", minutes, seconds];
lblCountDown.text = timerOutput;
//need to add a label for the next blind in the coredata list and update it while in a loop......
if (secondsCount == 0) {
[countdownTimer invalidate];
countdownTimer = nil;
}
}
-(void) setTimer{
// Configure and load the fetched results controller
self.model.frc_newTimer.delegate = self;
self.model.frc_newTimer.fetchRequest.predicate = [NSPredicate predicateWithFormat:#"timerName LIKE %#", #"Sample Timer"];
//add code to get the first coredata item in the blinds list
secondsCount = 240; // i need to insert the CoreData Blinds HERE
countdownTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(timerRun) userInfo:nil repeats:YES];
}
and buttons (yet to be fully sorted) to start actions
- (IBAction)StartTimer:(id)sender
{
[self setTimer];
}
- (IBAction)ResetTimer:(id)sender {
[countdownTimer invalidate];
countdownTimer = nil;
secondsCount = 0;
lblCountDown.text = #"00:00";
}

Answer 1

I'm assuming that you're running the countdown for a known Timer. In this case you don't need a fetch request as you have a relationship from the Timer to its set of Times, we can access it directly:
NSSet *times = self.myTimer.times;
We want to sort it so you can run the durations in some order:
(you might also want to check that the count of times > 0)
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"duration" ascending:YES];
NSArray *orderedTimes = [times sortedArrayUsingDescriptors:#[ sortDescriptor ]];
Next, we're going to need an instance variable to track where we are:
#property (assign, nonatomic) NSInteger currentTimeIndex;
With these parts, you can manage the process, and use an NSTimer to actually do the work. When the timer fires you go back to the time, get and sort the times, increment the index we're using, check the index is in range, get the duration and start the timer.
I'm going to be cheeky and say that if the expiring timer is nil, that means we're starting the process from scratch (it would be better to take the first case out into a specific method):
- (void)timerFired:(NSTimer *)expiringTimer
{
[expiringTimer invalidate];
NSInteger index = (expiringTimer != nil ? (self.currentTimeIndex + 1) : 0);
NSSet *times = self.myTimer.times;
if (times.count < index) {
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"duration" ascending:YES];
NSArray *orderedTimes = [times sortedArrayUsingDescriptors:#[ sortDescriptor ]];
double duration = [[[orderedTimes objectAtIndex:index] duration] doubleValue];
[NSTimer scheduledTimerWithTimeInterval:duration target:self selector:#selector(timerFired:) userInfo:nil repeats:NO];
} else {
// deal with the error
}
}
Now you can start the countdown with [self timerFired:nil];
You haven't said what you're doing while the timers are running, that could change things quite a bit (like you want to display an update of the time on screen each second)...
If you need to fetch the timer from your Core Data DB, that's where the fetch request comes in:
NSManagedObjectContext *context = <#Managed object context#>;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Timer"];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"timerName LIKE %#", #"Sample Timer"]];
NSArray *timers = [context executeFetchRequest:fetchRequest error:nil]; // should really add the error...
Timer *myTimer = nil;
if (timers.count == 1) {
myTimer = [timers lastObject];
} else {
// we didn't find the timer, agh!
}