iOS中NSString转换成HEX（十六进制）-NSData转换成int

 NSString *str = @"0xff055008";
 //先以16为参数告诉strtoul字符串参数表示16进制数字，然后使用0x%X转为数字类型
 unsigned long red = strtoul([str UTF8String],0,16);
 //strtoul如果传入的字符开头是“0x”,那么第三个参数是0，也是会转为十六进制的,这样写也可以：
 unsigned long red = strtoul([@"0x6587" UTF8String],0,0);
 NSLog(@"转换完的数字为：%lx",red);

 // 十六进制转换为普通字符串的。
 + (NSString *)stringFromHexString:(NSString *)hexString { //

 charchar *myBuffer = (charchar *)malloc((int)[hexString length] / 2 + 1);
 bzero(myBuffer, [hexString length] / 2 + 1);
 for (int i = 0; i < [hexString length] - 1; i += 2) {
 unsigned int anInt;
 NSString * hexCharStr = [hexString substringWithRange:NSMakeRange(i, 2)];
 NSScanner * scanner = [[[NSScanner alloc] initWithString:hexCharStr] autorelease];
 [scanner scanHexInt:&anInt];
 myBuffer[i / 2] = (char)anInt;
 }
 NSString *unicodeString = [NSString stringWithCString:myBuffer encoding:4];
 NSLog(@"------字符串=======%@",unicodeString);
 return unicodeString;


 }

 //普通字符串转换为十六进制的。

 + (NSString *)hexStringFromString:(NSString *)string{
 NSData *myD = [string dataUsingEncoding:NSUTF8StringEncoding];
 Byte *bytes = (Byte *)[myD bytes];
 //下面是Byte 转换为16进制。
 NSString *hexStr=@"";
 for(int i=0;i<[myD length];i++)

 {
 NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数

 if([newHexStr length]==1)

 hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];

 else

 hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
 }
 return hexStr;
 }

 //int 转data
 int i = 1;
 NSData *data = [NSData dataWithBytes: &i length: sizeof(i)];
 //data 转int
 int i;
 [data getBytes: &i length: sizeof(i)];