Question

This seems to be a perfectly valid program:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {

    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];

    NSString* hey = @"hey"
    @"there";
    NSLog(@"%@",hey);

    [pool drain];
    return 0;
}

Compiling this in llvm gcc and apple llvm shows no warnings or errors. Why? It seems one should be warned about this, as I can only see this as chaos-inducing. Especially in a situation like this:

NSArray* a = [NSArray arrayWithObjects:@"one",
              @"two,
              @"three
              @"four",
              nil];

You’d expect four entries…but no! Tricky, huh? Is it because you may want to split your string definition across multiple lines?

Answer 1

It’s a syntax for multi-line strings in Objective-C.

I cannot definitively answer why the language designer(s) designed it that way, but we can probably assume that they wanted the syntax for Objective-C strings to be analogous to the syntax for C strings.

That is, in C you can do the following for a multi-line string:

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

And in Objective-C, you can do the following for a multi-line string:

NSString *my_string = @"Line1 "
                      @"Line2"; // The @ on this line is optional.

(Code snippets adapted from https://stackoverflow.com/a/797351/25295)