Random alphanumeric case-sensitive ID generator in Objective C

IdGenerator.h

//
//  IdGenerator.h
//  
//
//  Created by Noah Santorello on 2/22/12.
//  Copyright (c) 2012 Noah Santorello. All rights reserved.
//

@interface IdGenerator : NSObject

// Generates a string containing 0-9, A-Z, a-z of the specified length
+(NSString*)randomId:(int)length;

@end

IdGenerator.m

//
//  IdGenerator.m
//  
//
//  Created by Noah Santorello on 2/22/12.
//  Copyright (c) 2012 Noah Santorello. All rights reserved.
//

#import "IdGenerator.h"

@implementation IdGenerator

+(NSString*)randomId:(int)length
{
    char bytes[length+1];
    
    for (int i = 0; i < length; i++)
    {
        int place = arc4random() % 62;
        place = place < 0 ? -place : place;
        if (place < 10)
        {
            // For 0-9
            bytes[i] = place + '0';
        }
        else if (place < 36)
        {
            // For A-Z
            bytes[i] = place + 'A' - 10;
        }
        else
        {
            // For a-z
            bytes[i] = place + 'a' - 36;
        }
    }
    bytes[length] = 0;
    
    return [NSString stringWithCString:bytes encoding:NSASCIIStringEncoding];
}

@end

Nice! =)