How to split a string literal across multiple lines in C / Objective-C?

There's a trick you can do with the pre-processor.
It has the potential down sides that it will collapse white-space, and could be confusing for people reading the code.
But, it has the up side that you don't need to escape quote characters inside it.

#define QUOTE(...) #__VA_ARGS__
const char *sql_query = QUOTE(
    SELECT word_id
    FROM table1, table2
    WHERE table2.word_id = table1.word_id
    ORDER BY table1.word ASC
);

the preprocessor turns this into:

const char *sql_query = "SELECT word_id FROM table1, table2 WHERE table2.word_id = table1.word_id ORDER BY table1.word ASC";

I've used this trick when I was writing some unit tests that had large literal strings containing JSON. It meant that I didn't have to escape every quote character \".

There are two ways to split strings over multiple lines:

1. Each string on its own line. Works only with strings:

   • Plain C:

     char *my_string = "Line 1 "
                       "Line 2";
     

   • Objective-C:

     NSString *my_string = @"Line1 "
                            "Line2";    // the second @ is optional
     

2. Using \ - can be used for any expression:

   • Plain C:

     char *my_string = "Line 1 \
                        Line 2";
     

   • Objective-C:

     NSString *my_string = @"Line1 \
                             Line2";
     

---

The first approach is better, because there isn't a lot of whitespace included. For a SQL query however, both are possible.

NOTE: With a #define, you have to add an extra \ to concatenate the two strings:

Plain C:

#define kMyString "Line 1"\
                  "Line 2"

I am having this problem all the time, so I made a tiny tool to convert text to an escaped multi-line Objective-C string:

http://multilineobjc.herokuapp.com/

Hope this saves you some time.

You could also go into XCode -> Preferences, select the Indentation tab, and turn on Line Wrapping.

That way, you won't have to type anything extra, and it will work for the stuff you already wrote. :-)

One annoying thing though is...

if (you're long on indentation
    && short on windows) {
            then your code will
                end up squished
                     against th
                         e side
                             li
                              k
                              e

                              t
                              h
                              i
                              s
}