A category for NSData that returns a hex string of the data within. Output is like: af459a2f

NSData+HexString.h

//
//  NSData+HexString.h
//
//  Copyright (c) 2013, Leigh McCulloch. All rights reserved.
//  BSD-2-Clause License: http://opensource.org/licenses/BSD-2-Clause
//

#import <Foundation/Foundation.h>

@interface NSData (HexString)

- (NSString *)hexString;

@end

NSData+HexString.m

//
//  NSData+HexString.m
//
//  Copyright (c) 2013, Leigh McCulloch. All rights reserved.
//  BSD-2-Clause License: http://opensource.org/licenses/BSD-2-Clause
//

#import "NSData+HexString.h"

@implementation NSData (HexString)

- (NSString *)hexString {
	NSMutableString *hex = [NSMutableString stringWithCapacity:[self length]*2];
	[self enumerateByteRangesUsingBlock:^(const void *bytes, NSRange byteRange, BOOL *stop) {
		const unsigned char *dataBytes = (const unsigned char *)bytes;
		for (NSUInteger i = byteRange.location; i < byteRange.length; ++i) {
			[hex appendFormat:@"%02x", dataBytes[i]];
		}
	}];
	return hex;
}

@end