Objective-C: Sort array using arguments

Question

I'm trying to sort an array passing an argument to the selector. For instance, I have an array of locations and I want to sort this array based on the distance they have from a certain point (for instance, my current location).

This is my selector, however I don't know how to call it.

- (NSComparisonResult)compareByDistance:(POI*)otherPoint withLocation:(CLLocation*)userLocation {
    int distance = [location distanceFromLocation:userLocation];
    int otherDistance = [otherPoint.location distanceFromLocation:userLocation];

    if(distance > otherDistance){
        return NSOrderedAscending;
    } else if(distance < otherDistance){
        return NSOrderedDescending;
    } else {
        return NSOrderedSame;
    }
}

I'm trying to sort the array using the following function, but I can't pass my location to the selector:

- (NSArray*)getPointsByDistance:(CLLocation*)location
{
    return [points sortedArrayUsingSelector:@selector(compareByDistance:withLocation:)];
}

Anomie · Accepted Answer · 2011-03-30 02:30:34Z

9

Besides sortedArrayUsingFunction:context: (already well explained by Vladimir), if you're targeting iOS 4.0 and up you could use sortedArrayUsingComparator:, as the passed location can be referenced from within the block. It would look something like this:

- (NSArray*)getPointsByDistance:(CLLocation*)location
{
    return [points sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
        int distance = [a distanceFromLocation:location];
        int otherDistance = [b distanceFromLocation:location];

        if(distance > otherDistance){
            return NSOrderedAscending;
        } else if(distance < otherDistance){
            return NSOrderedDescending;
        } else {
            return NSOrderedSame;
        }
    }];
}

You could, of course, call your existing method from within the block if you so desire.

answered Mar 30, 2011 at 2:30

Anomie

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2 Comments

Chuck Over a year ago

A block is a really nice solution here IMO.

ffleandro Over a year ago

this solution is exactly what I was trying to do. Vladimir's solution gets the job done, but this one is prettier ;)

Vladimir · Accepted Answer · 2011-03-29 12:24:28Z

2

Probably it will be more convenient to sort array using sortedArrayUsingFunction:context: method in your case. You can even utilise comparing selector you already have:

NSComparisonResult myDistanceSort(POI* p1, POI* p2, void* context){
     return [p1 compareByDistance:p2 withLocation:(CLLocation*)context];
}
...
- (NSArray*)getPointsByDistance:(CLLocation*)location
{
    return [points sortedArrayUsingFunction:myDistanceSort context:location];
}

answered Mar 29, 2011 at 12:24

Vladimir

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