Question

I have this code in Javascript:

var f = chr(50) + chr(0) + chr(1) + chr(64) + chr(24) + chr(0) + chr(0) + chr(1) + chr(159) + chr(13) + chr(0) + chr(0) + chr(224) + chr(7);

function chr(AsciiNum) {
    return String.fromCharCode(AsciiNum);
}

console.log outputs this as

2@
à 

With a length of 14.

I am trying to port it to Objective C.
I tried doing the following:

NSString *f = [NSString stringWithFormat:@"%c%c%c%c%c%c%c%c%c%c%c%c%c%c",50, 0 ,1, 64 , 24 , 0 , 0 , 1, 159,  13 , 0 , 0 , 224 , 7];

But I received a different output to the javascript code when using NSLog:

2@ü

What am I doing wrong? Is a character set issue?

Answer 1

Well, it seems that your problems stem from the fact that NSString’s ASCII support is limited to a strict 7-bit ASCII encoding, which means only the chars 0-127 are supported. You’ll have to use a different data type to store your chars, and that different data type is unichar, which supports 2^15-1 precisely because it is unsigned short. However, you will need to convert it to an NSString which operates in Unicode with this category:

@interface NSString (MNNSStringWithUnichar)
+ (NSString *) stringWithUnichar: (unichar) value;
@end

@implementation NSString (MNNSStringWithUnichar)

+ (NSString *) stringWithUnichar:(unichar) value {
     NSString *str = [NSString stringWithFormat: @"%C", value];
     return str;
}
@end

Or simply NSLog(@"%C", value);