Test for http://mortoray.com/2013/11/27/the-string-type-is-broken/ in Objective-C

broken-strings.m

#import <Foundation/Foundation.h>

@interface NSString (Reversing)
- (NSString *)reverseString;
@end

@implementation NSString (Reversing)
- (NSString *)reverseString;
{
	NSMutableString *reversedString = [NSMutableString stringWithCapacity:[self length]];

	[self enumerateSubstringsInRange:NSMakeRange(0, [self length]) 
	                         options:(NSStringEnumerationReverse | NSStringEnumerationByComposedCharacterSequences)
	                      usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
	                          [reversedString appendString:substring];
	                      }];
	return reversedString;
}
@end

int main(int argc, char *argv[]) {
	@autoreleasepool {
		NSString *str = nil;
		
		str = @"noël"; // decomposed
		NSLog(@"=== %@ ===", str);
		NSLog(@"%@", [str reverseString]); // expect lëon
		NSLog(@"%@", [str substringToIndex:3]); // expect noë
		NSLog(@"%tu", [str length]); // expect 4
		
		str = @"😸😾"; // emoji
		NSLog(@"=== %@ ===", str);
		NSLog(@"%@", [str reverseString]); // expect 😾😸
		NSLog(@"%@", [str substringFromIndex:1]); // expect 😾
		NSLog(@"%tu", [str length]); // expect 2
		
		str = @"baffle"; // with ligature
		NSLog(@"=== %@ ===", str);
		NSLog(@"%@", [str uppercaseString]); // expect BAFFLE
	}
}