How to convert HEX to NSString in Objective-C? - iphone

Question

I have a NSString with hex string like "68656C6C6F" which means "hello".
Now I want to convert the hex string into another NSString object which shows "hello". How to do that ?

Answer 1

I am sure there are far better, cleverer ways to do this, but this solution does actually work.
NSString * str = #"68656C6C6F";
NSMutableString * newString = [[[NSMutableString alloc] init] autorelease];
int i = 0;
while (i < [str length])
{
NSString * hexChar = [str substringWithRange: NSMakeRange(i, 2)];
int value = 0;
sscanf([hexChar cStringUsingEncoding:NSASCIIStringEncoding], "%x", &value);
[newString appendFormat:#"%c", (char)value];
i+=2;
}

Answer 2

This should do it:
- (NSString *)stringFromHexString:(NSString *)hexString {
// The hex codes should all be two characters.
if (([hexString length] % 2) != 0)
return nil;
NSMutableString *string = [NSMutableString string];
for (NSInteger i = 0; i < [hexString length]; i += 2) {
NSString *hex = [hexString substringWithRange:NSMakeRange(i, 2)];
NSInteger decimalValue = 0;
sscanf([hex UTF8String], "%x", &decimalValue);
[string appendFormat:#"%c", decimalValue];
}
return string;
}

Answer 3

+(NSString*)intToHexString:(NSInteger)value
{
return [[NSString alloc] initWithFormat:#"%lX", value];
}

Answer 4

extension String {
func hexToString()-> String {
var newString = ""
var i = 0
while i < self.count {
let hexChar = (self as NSString).substring(with: NSRange(location: i, length: 2))
if let byte = Int8(hexChar, radix: 16) {
if (byte != 0) {
newString += String(format: "%c", byte)
}
}
i += 2
}
return newString
}
}

Answer 5

I think the people advising initWithFormat is the best answer as it's objective-C rather than a mix of ObjC, C.. (although the sample code is a bit terse).. I did the following
unsigned int resInit = 0x1013;
if (0 != resInit)
{
NSString *s = [[NSString alloc] initWithFormat:#"Error code 0x%lX", resInit];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Initialised failed"
message:s
delegate:nil
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[alert show];
[alert release];
[s release];
}