Sort an array with numeric strings

Question

Hello I have an array of persons, and i am trying to sort them by age using a sort descriptor. The age field in a patient is a string so when calling:

ageSorter = [[NSSortDescriptor alloc] initWithKey:@"age" ascending:YES];
[personList sortUsingDescriptors:[NSArray arrayWithObject:ageSorter]];

It sorts them but 100 appears first because its is not using numericSearch in the compare options.

Is there a ways i can still sort with descriptor but maybe using a selector to change how to compare the strings?

Answer 1

You could create a category on NSString that adds a method numericCompare: and which calls [self compare:otherString options:NSNumericSearch]. Another option is to convert the age field into a NSNumber instead of a NSString. Yet another option involves a NSComparator block and sortUsingComparator.

Answer 2

The finderSortWithLocale method (both these are taken from apple api):

int finderSortWithLocale(Person *person1, Person *person2, void *locale)
{
    static NSStringCompareOptions comparisonOptions = NSNumericSearch;

    NSRange string1Range = NSMakeRange(0, [string1 length]);
    NSString *age1 = person1.age;
    NSString *age2 = person2.age;
    return [age1 compare:age2
                    options:comparisonOptions
                    range:string1Range
                    locale:(NSLocale *)locale];
}

How to call this method (edited: call the function on array of Persons):

    NSArray *sortedArray = [personList sortedArrayUsingFunction:finderSortWithLocale
                                         context:[NSLocale currentLocale]];