sort NSInteger using sortUsingComparator

Question

I am trying to sort an array of NSObjects (a object is of a class). The object class has several variables which I am wanting to use to sort the objects in the array, the variables I am using to sort are of type NSString or NSInteger, I am confident I am sorting NSStrings but for this question I am hoping to get help for sorting a NSInteger.

This is the method I am using to sort the array of objects, It receives an NSMutableArray of objects

- (NSMutableArray *)startSortingTheArray:(NSMutableArray *)unsortedArray
{
    [unsortedArray sortUsingComparator:^ NSComparisonResult(SearchResultItem *d1, SearchResultItem *d2) {
        NSInteger DoorID1 = d1.doorID;
        NSInteger DoorID2 = d2.doorID;
        NSComparisonResult result = [DoorID1 localizedCompare:DoorID2]; // Not sure how to sort these two integers
        if (result == NSOrderedSame) {
            NSString *handel1 = d1.handel;
            NSString *handel2 = d2.handel;
            result = [handel1 localizedCompare:handel2];
         }

I am not sure how to compare the NSInteger, I have read that I could minus each number from itself.. if the number is 0 then they are equal or +1 / -1 etc they are not.. but not sure if thats the best way to approach this.

any help would be appreciated.

Solution 1

[unsortedArray sortUsingComparator:^ NSComparisonResult(SearchResultItem *d1, SearchResultItem *d2) {
    NSInteger doorID1 = d1.doorID;
    NSInteger doorID2 = d2.doorID;
    if (doorID1 < doorID2)
        return NSOrderedAscending;
    if (doorID1 > doorID2)
        return NSOrderedDescending;
    return [d1.handel localizedCompare: d2.handel];
}];

as [aString localizedCompare:anotherString] will return NSOrdered(Ascending|Descending|same), you can just return its result for the string case.

Solution 2

An NSInteger is not an object. It is just an integer (either an int or a long). So you can compare them exactly how you would compare two ints.

Classic C comparison functions allow you to do the x - y trick, but that's not appropriate here since you'd be returning an integer that doesn't fit into the NSComparisonResult enum. As such, you should probably just do something like

if (DoorID1 == DoorID2) {
    // compare secondary attribute
    NSString *handel1 = d1.handel;
    NSString *handel2 = d2.handel;
    return [handel1 localizedCompare:handel2];
}
else if (DoorID1 < DoorID2) return NSOrderedAscending;
else return NSOrderedDescending;

Incidentally, your sorting criteria can be represented with NSSortDescriptor instead, which may be clearer.

- (NSMutableArray *)startSortingTheArray:(NSMutableArray *)unsortedArray {
    NSSortDescriptor *primary = [NSSortDescriptor sortDescriptorWithKey:@"doorID" ascending:YES];
    NSSortDescriptor *secondary = [NSSortDescriptor sortDescriptorWithKey:@"handel" ascending:YES selector:@selector(localizedCompare:)];
    [unsortedArray sortUsingDescriptors:@[primary, secondary]];
}

Solution 3

Another option:

NSComparisionResult res = [@(d1.doorID) compare:@(d2.doorID)];
return res == NSOrderedSame ? [d1.handel localizedCompare: d2.handel] : res;

Solution 4

[unsortedArray sortUsingComparator:^ NSComparisonResult(SearchResultItem *d1, SearchResultItem *d2) {
    NSInteger doorID1 = d1.doorID;
    NSInteger doorID2 = d2.doorID;
    if (doorID1 > doorID2)
        return NSOrderedAscending;
    if (doorID1 < doorID2)
        return NSOrderedDescending;
    if (doorID1==doorID2) {
        NSString *s1=d1.someString;
        NSString *s2=d2.someString;
        return [s1 compare:s2];
    }
}

View more solutions

Comments

[HurkNburkS]

say for instance I have to move onto the next if statment for the string if NSOrderedSame then how do I do that? where dose return return too?

[HurkNburkS]

If NSOrderedSame occurs how to I step onto the next section of code ? (i.e. compare a string) as I am not sure where return is returning from...

[HurkNburkS]

okay I understand whats happening here.. will give this ago now.. :) will let you know how I get on :P

[Lily Ballard]

@HurkNburkS: The return is returning from the block.

[vikingosegundo]

note that the last if statement is not necessary, as the integers must be equal. in fact this might lead to a warning or error, as the compiler must assume, that none return statement will be reached — what is impossible.

[HurkNburkS]

with regards to your sort descriptor, how dose that work? dose it sort the array based on primary first then secondary? also dose it account for NSString or NSInteger types?

[Bogdan Andresyuk]

You`re right, its late here..just wanted to show to HurkNburkS how this all works, as he could not get the point of last return statement

[HurkNburkS]

okay thank you.. I kinda see what your doing here.. however I think my problem stems from the fact I am trying to sort based on several different if variables, a mixture of NSString and NSInteger, so I am trying to figure out the format of how you have written your solution based on more variables than just the two.

[vikingosegundo]

just do it with nested if-statements. You dont need to return immediately.

[HurkNburkS]

@vikingosegundo yes for this example you are correct, however It is actually what I need as I have several other variables I am sorting with not just the two in my example. so it is actually useful if I want to move onto checking more variables

[HurkNburkS]

okay.. I am currently working on a solution based off everyones help atm.. so will come back with an answer shortly.

[HurkNburkS]

Okay it seems to be working.. I have to run more tests on it but looks like it's sorted.. this post helped me the most so far thats why I have selected it...

[Lily Ballard]

@HurkNburkS: Yes, it sorts by the first sort descriptor, and only goes to the next one if the first one returned NSOrderedSame. It also uses -valueForKey: internally, which will automatically wrap NSIntegers in NSNumbers, which supports -compare:. The first sort descriptor will use -compare: implicitly, the second one is explicitly using -localizedCompare:.

[terphi]

@vikingosegundo I think you have the NSOrderedAscending and NSOrderedDescending cases mixed up. I had to reverse them to get the correct insertion index for the NSBinarySearchingInsertionIndex case.