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Sort NSmutableArray that contains 2 types of object?

I have an NSMutableArray that contains 2 types of objects.

Both objects contain a field for dates (string of strings in different formats) with different names.

What is the best and fastest way to sort them by date? Is it possible to use NSSortDescriptorin this situation?

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2 answers

If you are targeting Mac OS X v10.6 or iOS4 and later, you can sort using a comparator like this

NSDateFormatter *formatter1 = ...; //create and configure date formatter for Class1
NSDateFormatter *formatter2 = ...; //create and configure date formatter for Class2


[arrayOfObjects sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    NSDate *date1 = nil, *date2 = nil;
    //Get first objects date
    if([obj1 isKindOfClass:[Class1 class]])
    {
        date1 = [formatter1 dateFromString:[obj1 class1Date]];
    }
    else if([obj1 isKindOfClass:[Class2 class]])
    {
        date1 = [formatter2 dateFromString:[obj1 class2Date]];
    }

    //Get second objects date
    if([obj2 isKindOfClass:[Class1 class]])
    {
        date2 = [formatter1 dateFromString:[obj2 class1Date]];
    }
    else if([obj2 isKindOfClass:[Class2 class]])
    {
        date2 = [formatter2 dateFromString:[obj2 class2Date]];
    }

    NSAssert(date1 != nil, @"Could not parse date from %@", obj1);
    NSAssert(date2 != nil, @"Could not parse date from %@", obj2);

    return [date1 compare:date2];
}];

Besides checking the class, you can also check if it responds to the selector.

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, . , A "dateString", B "createDateString"... :

@implementation A (SortByDate)

-(NSDate*)sortDate
{
    static NSDateFormatter * formatter = nil ;
    static dispatch_once_t once = 0 ;
    dispatch_once( & once, ^{ formatter = ... } ) ;

    return [ formatter dateFromString:self.dateString ] ;
}
@end

@implementation B (SortByDate)
-(NSDate*)sortDate
{
    static NSDateFormatter * formatter = nil ;
    static dispatch_once_t once = 0 ;
    dispatch_once( & once, ^{ formatter = ... } ) ;

    return [ formatter dateFromString:self.creationDateString ] ;
}
@end

sortDate:

NSArray * sortedByDateArray = [ unsortedArray sortedArrayUsingComparator:^( id a, id b ){
    return [ [ a sortDate ] compare:[ b sortDate ] ] ;
}];

EDIT :

NSArray * sortedArray = [ unsortedArray sortedArrayUsingDescriptors:[ NSArray arrayWithObject:[ NSSortDescriptor sortDescriptorWithKey:@"sortDate" ascending:YES ] ] ] ;
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