Question

I get an array of strings with the following strings, there is a certain patern to the strings

str1
str51
str3
str4
str10
str39
str31
str191

Every string starts with ‘str’ and has a number appended onto the end of it.

Is there a neath way to sort the array so it lists the strings in order of value

str1
str3
str4
str10
str31
str39
str51
str191

I can see a way to do it by writing some recursive function that will

NSString * firstString = [[strArray objectAtIndex:i].substringFromIndex:3];
NSString * secondString = [[strArray objectAtIndex:i+1].substringFromIndex:3];

if ([firstString intValue] < [secondString intValue])
{
    //do nothing they order is correct
}
else
{
    //swap the order of the 2 strings in the array
}

But thats very rudimentary code, Is there some mechanism in Objective-C or a nice code trick to handle this sorting better?

Many Thanks,
-Code

Answer 1

If they all start with the same prefix, I believe that the default sort will handle them appropriately. By this, I mean:

[someArray sortUsingSelector:@selector(compare:)];

If, for some reason, this isn’t working, then you can use a block. Try this:

NSArray *sortedArray = [someArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) 
{
    //Default compare, to protect against cast
    if (![a isKindOfClass:[NSString class]] || ![b isKindOfClass:[NSString class]]) {
        return ([a compare:b]);
    }
    else {
        NSString *aString = (NSString*) a;
        NSString *bString = (NSString*) b;
        int aInt = [[a.substringFromIndex:3] intValue];
        int bInt = [[b.substringFromIndex:3] intValue];
        return [aInt < bInt];
    }
}];