将 HEX NSString 转换为 ASCII NSString

Question

我得到一个包含 十六进制值 的 NSString，我想将其转换为 ASCII。我该怎么做？

NSString * hexString = // some value
NSString * asciiString = // ? convert hexString to ASCI somehow

---

我尝试的方法不正确：

我尝试了在similar question 上找到的以下方法，但它对我不起作用：

   NSData *_data = [hexString dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableString *_string = [NSMutableString stringWithString:@""];
    for (int i = 0; i < _data.length; i++) {
        unsigned char _byte;
        [_data getBytes:&_byte range:NSMakeRange(i, 1)];
        if (_byte >= 32 && _byte < 127) {
            [_string appendFormat:@"%c", _byte];
        } else {
            [_string appendFormat:@"[%d]", _byte];
        }
    }
    asciiString = _string; // Still shows the same as before..

Answer 1

这对我有用：

NSString * str = @"312d4555";
NSMutableString * newString = [[NSMutableString alloc] init];
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;
}
NSLog(@"%@", newString);

输出是：你好