How to compare current system time with an array of times - ios

Question

I am using the below code to try and use current system time to tell me the next time in the array. All it logs out is the last number in the array. I have searched, and this is how I ended up where I am, but could never get it to work just right. Thanks
self.array = #[#"00:15", #"01:35, "#"05:30", #"06:10", #"07:05", #"07:55", #"08:45", #"09:35", #"10:40", #"11:25", #"12:20", #"13:10", #"14:05", #"15:00", #"15:45", #"16:40", #"17:30", #"18:20", #"19:20", #"20:10", #"21:00", #"22:05", #"22:55"];
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"HH:mm"];
NSDate *formattedCurrentDate = [dateFormat dateFromString:[dateFormat stringFromDate:[NSDate date]]];
for(NSString *stringTime in self.array) {
NSDate *dateFromString = [dateFormat dateFromString:stringTime];
if([formattedCurrentDate earlierDate:dateFromString]) {
self.nextTime.text = stringTime;
}
}

Answer 1

Your code is behaving exactly as it should, you are having it return an earlier time than the current time, which means every single time is assigned to self.nextTime.text, but you only see the very last assignment, which is the last item in the array.
Further more your if statement always returns true if executed correctly, so you will always get true unless you provide an object that is not an NSDate.
Here is the correct way of getting what you would like without having to worry about ordering your array.
NSArray *array = #[#"16:40", #"05:30", #"06:10", #"07:05", #"07:55", #"08:45", #"09:35", #"10:40", #"11:25", #"12:20", #"13:10", #"14:05", #"15:00", #"15:45", #"16:40", #"17:30", #"18:20", #"19:20", #"20:10", #"21:00", #"22:05", #"22:55", #"23:55", #"01:35"];
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"HH:mm"];
NSDate *formattedCurrentDate = [dateFormat dateFromString:[dateFormat stringFromDate:[NSDate date]]];
NSDate *laterDate;
NSDate *closestDate;
for(NSString *stringTime in array) {
NSDate *dateFromString = [dateFormat dateFromString:stringTime];
laterDate = [formattedCurrentDate laterDate:dateFromString];
if(![laterDate isEqualToDate:formattedCurrentDate]){
closestDate = [laterDate earlierDate:closestDate];
}
}
NSLog(#"Closest Date: %#", [dateFormat stringFromDate:closestDate] );

Answer 2

NSArray *array = #[#"23:15", #"01:35", #"05:30", #"06:10", #"07:05", #"07:55", #"08:45", #"09:35", #"10:40", #"11:25", #"12:20", #"13:10", #"14:05", #"15:00", #"15:45", #"16:40", #"17:30", #"18:20", #"19:20", #"20:10", #"21:00", #"22:05", #"22:55", #"23:55"];
NSMutableArray *datesArray = [[NSMutableArray alloc] init];
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"HH:mm"];
//Convert all strings to dates
for (NSString *str in array)
{
NSDate *formattedCurrentDate = [dateFormat dateFromString: str];
[datesArray addObject:formattedCurrentDate];
}
//Sort dates.
NSArray *sortedArray = [datesArray sortedArrayUsingSelector:#selector(compare:)];
NSString *date = [dateFormat stringFromDate:[NSDate date]];
NSDate *formattedTodatDate = [dateFormat dateFromString:date];
//Print the desired date
for(NSDate *stringTime in sortedArray)
{
if([formattedTodatDate compare:stringTime] == NSOrderedAscending)
{
NSLog(#"Result is %#", [dateFormat stringFromDate:stringTime]);
break;
}
}
Try the above code. I just followed what others have mentioned with sorting dates.

Answer 3

If you want a more generic solution, that doesn't depend on the order of the array, you could use the code below:
NSArray *array = #[#"02:25", #"01:35", #"05:30", #"06:10", #"07:05", #"07:55", #"08:45", #"09:35", #"10:40", #"11:25", #"12:20", #"13:10", #"14:05", #"15:00", #"15:45", #"16:40", #"17:30", #"18:20", #"19:20", #"20:10", #"21:00", #"22:05", #"22:55", #"23:55"];
NSDateFormatter *dateFormat = [NSDateFormatter new];
[dateFormat setDateFormat:#"HH:mm"];
NSDate *formattedCurrentDate = [dateFormat dateFromString:[dateFormat stringFromDate:[NSDate date]]];
NSTimeInterval currentInterval = [formattedCurrentDate timeIntervalSince1970];
NSTimeInterval smallerInterval = CGFLOAT_MAX;
for(NSString *stringTime in array) {
NSDate *dateFromString = [dateFormat dateFromString:stringTime];
NSTimeInterval dateFromStringInterval = [dateFromString timeIntervalSince1970];
NSTimeInterval actualInterval = (dateFromStringInterval - currentInterval);
if(actualInterval > 0 && actualInterval < smallerInterval){
smallerInterval = actualInterval;
self.nextTime.text = stringTime;
}
}
This code is getting the closest next hour of the current hour, independent of it's index inside the array. And doesn't require more allocations or any sorting of arrays, like #Sandeep solutions (that do works).
Explaining:
The actualInterval is getting the difference in seconds between all dates and the current date. This variable (which is a double, actually) will only be positive to future hours (past hours will be negative).
So, all the code is doing is getting the smaller difference between future hours. This is, I think, the best solution to this case.
Hope this helped.

Answer 4

if your function works fine.
change:
for(NSString *stringTime in self.array) {
NSDate *dateFromString = [dateFormat dateFromString:stringTime];
if([formattedCurrentDate earlierDate:dateFromString]) {
self.nextTime.text = stringTime;
}
}
to:
for(NSString *stringTime in self.array) {
NSDate *dateFromString = [dateFormat dateFromString:stringTime];
if([formattedCurrentDate compare:dateFromString] == NSOrderedAscending) {
self.nextTime.text = stringTime;
break;
}
}