My objects have a timestamp and a text, the timestamp is a NSDate formatted to a NSString before saving. After creating a new object and setting its values I save it. Later when loading it I put all objects into an Array and mix that Array with another Array, thats why I need to sort the Array.
My problem is: I don't know how to properly sort the Array by the object's timestamp property.
I have been searching a lot but still don't have an up-to-date-answer. Any help is appreciated.
3 Answers
To compare two different time stamp you have to convert it to NSData first:
-(NSDate)convertToDate:(NSString*)inputDate
//NSString *inputDate = @"11/20/2013 3:30:05 PM"; //<-- Your date probably is different than that
NSDateFormatter *dateFormatter1 = [[NSDateFormatter alloc] init];
dateFormatter1.dateFormat = @"MM/dd/yyyy hh:mm:ss a"; //<-- this needs to be changet to match your time stamp format
[dateFormatter1 setLocale:[NSLocale currentLocale]];
NSDate *date = [dateFormatter1 dateFromString:inputDate]; //<- this is your NSDate object.
return date;
}
NSArray *sortedArray = [unSortedArray sortedArrayUsingComparator: ^NSComparisonResult(DateObj *id1, DateObj *id2) {
NSDate d1 = [self convertToDate:id1.timeStamp];
NSDate d2 = [self convertToDate:id2.timeStamp];
return [d1 compare:d2];
}];
You can also add compare method to your class, for example:
- (NSComparisonResult)compare:(YourClass *)obj
{
NSDate d1 = [self convertToDate:self.timeStamp];
NSDate d2 = [self convertToDate:obj.timeStamp];
return [d1 compare:d2];
}
And if you need to sort array of this object you call:
NSArray *sortedArray = [yourArray sortedArrayUsingSelector:@selector(compare:)];
Comments
Try this;
NSArray *sortedArray = [unSortedArray sortedArrayUsingComparator: ^NSComparisonResult(DateObj *id1, DateObj *id2) {
if(id1.timeStamp > id2.timeStamp)
return NSOrderedAscending;
else if (id1.timeStamp < id2.timeStamp)
return NSOrderedDescending;
else return NSOrderedSame;
}];
You will get more about sorting HERE.
2 Comments
neilco
BOOL (which has two possible values) is not a synonym for NSComparisonResult (which has three possible values).
KethanKumar
Use loop to compare more than two values.
My solution:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd.MM.YYYY HH:mm:ss"];
NSMutableArray *timeStamps = [[NSMutableArray alloc] init];
for(Object *object in allObjects) {
NSDate *time = [dateFormatter dateFromString:object.timeStamp];
[timeStamps addObject:time];
}
[timeStamps sortedArrayUsingSelector:@selector(compare:)];
NSMutableArray *sortedArray = [NSMutableArray arrayWithCapacity:[allObjects count]];
for(int i = 0; i < [timeStamps count]; i++) {
for(Object *object in allObjects) {
if(object.timeStamp == [dateFormatter stringFromDate:timeStamps[i]]) {
[sortedArray addObject:messageObject];
}
}
}
return sortedArray;
sortedArrayUsingComparator:. In the comparator block, convert the NSString timestamps to NSDate objects andcompare:one to the other.