如何在Objective-C中将十六进制字符串（NSString）转为字节数组及NSArray

Hey there! Making the jump from Java/Android to iOS is a fun (and sometimes tricky) transition—let's sort out how to convert that hex string into the exact NSArray you're looking for, and also take a look at your current method to spot any issues.

First, Let's Break Down Your Goal #

You have a hex string:

NSString *code = @"11111bfb";

And you want to convert it to an NSArray of NSNumber objects representing each byte:

NSArray *codeArray = @[@0x11, @0x11, @0x1b, @0xfb];

Looking at Your Existing Method #

Your current dataFromHexString: method returns an NSData object, which is great for raw byte storage—but it doesn't directly give you the NSArray of NSNumbers you need. Additionally, there's a small issue with how it handles odd-length strings:

• When the string length is odd, you prepend @"0x", but strtoul treats 0x as a prefix for hex values, not as actual hex digits. This means for an odd-length string like @"1bfb", your code would turn it into @"0x1bfb" and then parse the first two characters ("0x") as 0, which isn't the correct way to pad the string (you should prepend a single 0 instead).

The Correct Implementation for Your Needs #

Here's a method that directly converts your hex string into the NSArray of NSNumber objects you're targeting:

- (NSArray<NSNumber *> *)hexStringToNumberArray:(NSString *)hexString {
    // Remove any spaces from the input string (in case they exist)
    hexString = [hexString stringByReplacingOccurrencesOfString:@" " withString:@""];
    NSUInteger stringLength = hexString.length;
    
    // Pad with a leading 0 if the string length is odd (so we can process in pairs)
    if (stringLength % 2 != 0) {
        hexString = [@"0" stringByAppendingString:hexString];
        stringLength += 1;
    }
    
    NSMutableArray *resultArray = [NSMutableArray arrayWithCapacity:stringLength / 2];
    
    // Iterate over the string two characters at a time
    for (NSUInteger i = 0; i < stringLength; i += 2) {
        NSString *byteSubstring = [hexString substringWithRange:NSMakeRange(i, 2)];
        NSScanner *scanner = [NSScanner scannerWithString:byteSubstring];
        unsigned int byteValue;
        
        // Parse the two-character hex substring into an integer
        [scanner scanHexInt:&byteValue];
        
        // Add the byte value as an NSNumber to the array
        // If you need signed bytes, cast to int8_t here: @((int8_t)byteValue)
        [resultArray addObject:@(byteValue)];
    }
    
    return resultArray;
}

How to Use It #

Call it with your example string:

NSString *code = @"11111bfb";
NSArray *codeArray = [self hexStringToNumberArray:code];
// codeArray will be @[@0x11, @0x11, @0x1b, @0xfb]—exactly what you want!

Key Improvements Over Your Original Method #

• Directly returns the NSArray type you need: No extra steps to convert from NSData to an array of NSNumbers.
• Correct padding for odd-length strings: Prepends a single 0 instead of 0x, ensuring valid hex digit pairs.
• Uses NSScanner for safe parsing: It's a more Objective-C-native way to handle hex conversion and avoids potential issues with C string manipulation.

内容的提问来源于stack exchange，提问作者Edward Tattsyrup