De-duplication of NSString & unichar constants

Question

I have two simple constants:

NSString and
unichar,

defined as follows:

static NSString * const string = @"\u2022";
static unichar const character = 0x2022;

I'd want to have the number 0x2022 defined in one place.

I tried a lot of combinations (# and ##, also CFSTR macro) with no success.

Can it be done?

What do you mean by "extracting a character"? – Ramy Al Zuhouri Aug 19 '13 at 18:06 — Ramy Al Zuhouri, Aug 19 '13 at 18:06
@RamyAlZuhouri I simplified the text. Hope it's clearer. – Rudolf Adamkovič Aug 19 '13 at 18:47 — Rudolf Adamkovič, Aug 19 '13 at 18:47

score 1 · Accepted Answer · edited May 23 '17 at 10:31

1

(Using ideas from How to concatenate twice with the C preprocessor and expand a macro as in "arg ## _ ## MACRO"?):

#define STRINGIFY(_x_) #_x_

#define UNICHAR_FROM_HEXCODE1(_c_) 0x ## _c_
#define UNICHAR_FROM_HEXCODE(_c_) UNICHAR_FROM_HEXCODE1(_c_)

#define NSSTRING_FROM_HEXCODE1(_c_) @"" STRINGIFY(\u ## _c_)
#define NSSTRING_FROM_HEXCODE(_c_) NSSTRING_FROM_HEXCODE1(_c_)

#define MYCHARCODE 2022
static unichar const character = UNICHAR_FROM_HEXCODE(MYCHARCODE);
static NSString * const string = NSSTRING_FROM_HEXCODE(MYCHARCODE);

Preprocessed output:

static unichar const character = 0x2022;
static NSString * const string = @"" "\u2022";

(Note that @"" "\u2022" is equivalent to @"\u2022".)

edited May 23 '17 at 10:31

Community

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answered Aug 19 '13 at 19:04

Martin R

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This works. It generates a warning though: _\u used with no following hex digits; treating as '\' followed by identifier_ for the 4th `#define`. – Rudolf Adamkovič Aug 19 '13 at 21:21
All right, I've figured it out. Simply pushed `ignored -Wunicode` for that one line. Thanks, man! Accepted. Perfect. – Rudolf Adamkovič Aug 19 '13 at 21:36

De-duplication of NSString & unichar constants

1 Answers1