representing time interval in objective-C - iphone

Question

I know that there is a data type called NSTimeInterval, but this is in seconds. I want to have an object representation that would be able to represent a time range, say Thursday 21 June 8:00 - Thursday 21 June 9:00. Later on I want to compare the current date/time and check whether it fits within this range. What is the best way to do this?

Answer 1

I would suggest using two NSDate objects to store the start and end dates. You can easily determine if a date is between them using the timeIntervalSinceDate: method:
- (BOOL)dateInInterval:(NSDate *)testDate {
// date1 is the instance variable containing the starting date
// date2 is the instance variable containing the ending date
return ([testDate timeIntervalSinceDate:date1] > 0 &&
[testDate timeIntervalSinceDate:date2] < 0);
}
You just need to make a class which holds two NSDate objects, making sure the first is before the second, and including this method.
FYI, NSTimeInterval is not a class, its a typedef of double.
Edit
Since you want use these as keys for a dictionary, you could use something similar to this to store and search your data:
#protocol IntervalDictionaryKey <NSObject>
// The class you use as keys for your dictionary must implement this method to determine if a object is in the interval
- (BOOL)intervalContains:(id)object;
#end
#interface IntervalDictionary : NSObject {
NSMutableArray *keys, *values;
}
- (void)addInterval:(id<IntervalDictionaryKey>)interval withObject:(id)object;
- (void)setObject:(id)object forIntervalOf:(id)intervalObject;
- (id)objectForIntervalOf:(id)object;
#end
#implementation IntervalDictionary
- (id)init {
if(self = [super init]) {
keys = [NSMutableArray new];
values = [NSMutableArray new];
}
return self;
}
- (void)dealloc {
[keys release];
[values release];
[super dealloc];
}
- (void)addInterval:(id<IntervalDictionaryKey>)interval withObject:(id)object {
[keys addObject:interval];
[values addObject:object];
}
- (void)setObject:(id)object forIntervalOf:(id)intervalObject {
id<IntervalDictionaryKey> key;
NSUInteger i = 0;
for(key in keys) {
if([key intervalContains:intervalObject]) {
[values replaceObjectAtIndex:i withObject:object];
break;
}
++i;
}
}
- (id)objectForIntervalOf:(id)object {
id<IntervalDictionaryKey> key;
NSUInteger i = 0;
for(key in keys) {
if([key intervalContains:object]) {
return [values objectAtIndex:i];
}
++i;
}
}
#end
Usage:
Example interval class:
#interface DateInterval : NSObject <IntervalDictionaryKey> {
NSDate *date1, *date2;
}
- (BOOL)intervalContains:(NSDate *)date; // this is the same as the dateInInterval method above
#end
#implementation DateInterval
// initializer which sets date1 and date2
- (BOOL)intervalContains:(NSDate *)date {
return ([date timeIntervalSinceDate:date1] > 0 &&
[date timeIntervalSinceDate:date2] < 0);
}
#end
Example usage code:
//intervalX is a DateInterval object, created elsewhere
//objectX is any object, created elsewhere
//objectInX is a NSDate which is part of intervalX, created elsewhere
IntervalDictionary *dict = [IntervalDictionary new];
[dict addInterval:interval0 withObject:object0];
[dict addInterval:interval1 withObject:object1];
[dict objectForIntervalOf:objectIn0]; // returns object0
[dict objectForIntervalOf:objectIn1]; // returns object1
[dict setObject:object2 forIntervalOf:objectIn1]; // changes the object for interval1 to object2
[dict objectForIntervalOf:objectIn1]; // now returns object2

Answer 2

NSDateComponents can be used to store components of time intervals as well as date components. You can add such an object to an NSDate using NSCalendar's dateByAddingComponents:toDate:options:.

Answer 3

From iOS10+ you have NSDateInterval (See https://developer.apple.com/documentation/foundation/nsdateinterval?language=objc).
Is the best data structure to represent a time interval.