NSDictionary sort by keys as floats

Question

basically I have an NSDictionary with keys and values.

The keys are all numbers, but at the moment they are strings.

I want to be able to compare them as numbers

Answer 1

Not sure what you are up to – dictionaries are inherently unsorted, there is no stable key ordering in the default implementation. If you want to walk the values by sorted keys, you can do something like this:

NSInteger floatSort(id num1, id num2, void *context)
{
    float v1 = [num1 floatValue];
    float v2 = [num2 floatValue];
    if (v1 < v2)
        return NSOrderedAscending;
    else if (v1 > v2)
        return NSOrderedDescending;
    else
        return NSOrderedSame;
}

NSArray *allKeys = [aDictionary allKeys];
NSArray *sortedKeys = [allKeys sortedArrayUsingFunction:floatSort context:NULL];
for (id key in sortedKeys)
    id val = [aDictionary objectForKey:key];
    …

Answer 2

Use compare:options: with NSNumericSearch.

Answer 3

You can't sort a dictionary, but you can get the keys as an array, sort that, then output in that order. sortedArrayUsingComparator will do that, and you can compare the strings with the NSNumericSearch option.

NSArray* keys = [myDict allKeys];
NSArray* sortedArray = [keys sortedArrayUsingComparator:^(id a, id b) { 
    return [a compare:b options:NSNumericSearch]; 
}]; 

for( NSString* aStr in sortedArray ) {
    NSLog( @"%@ has key %@", [myDict objectForKey:aStr], aStr );
}