Advanced Localization with Omission of Arguments in Xcode

Question

I have this formatted string that I am having a translator work on.

ENGLISH

\"Check out the %1$@ %2$@ in %3$@: %4$@\" = \"Check out the %1$@ %2$@ in         


        

Answer 1

Looks like a bug to me. I think you should file a bug.

CFString's formatting engine is independent from fprintf's so there could be some differences. For instance,

printf("a %3$s\n", "b", "c", "d"); // prints "a d"
NSLog(@"a %3$s\n", "b", "c", "d"); // prints "a b"

You need to supply all previous specifiers because the width of an argument doesn't need to be fixed, e.g

printf("%2$llx %1$llx\n", 1LL, 2LL); // prints "2 1"
printf("%2$llx\n", 1LL, 2LL);        // prints "200000000" !!
NSLog(@"%2$llx %1$llx\n", 1LL, 2LL); // prints "2 1"
NSLog(@"%2$llx\n", 1LL, 2LL);        // prints "1"

iPhone OS's printf skips 4 bytes on 1 missing specifier, and CFString's formatter skips 0 bytes.

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The solutions are:

3. Rearrange your indices, e.g.

   "Check out the %4$@ %1$@ in %2$@: %3$@"
   "Hör Dir mal %1$@ in %2$@ an: %3$@";
   

   or

4. use the format

   [@"%1$10p%2$10p%3$10p%4$10p" stringByAppendingString:frmt]
   

   to force all arguments to be used, and then chop out the first 40 characters with -substringFromIndex:, or

5. Convert all ObjC objects into C strings (char*) and use snprintf.

6. Write your own formatting engine.

Answer 2

This is not a bug. Numbered arguments are not part of the C standard, but part of IEEE Std 1003.1, which says the following (emphasis mine):

The format can contain either numbered argument conversion specifications (that is, "%n$" and "*m$"), or unnumbered argument conversion specifications (that is, % and * ), but not both. The only exception to this is that %% can be mixed with the "%n$" form. The results of mixing numbered and unnumbered argument specifications in a format string are undefined. When numbered argument specifications are used, specifying the Nth argument requires that all the leading arguments, from the first to the (N-1)th, are specified in the format string.