NSString to NSArray

NSMutableArray *letterArray = [NSMutableArray array];
NSString *letters = @"ABCDEF𝍱क्";
[letters enumerateSubstringsInRange:NSMakeRange(0, [letters length]) 
                            options:(NSStringEnumerationByComposedCharacterSequences) 
                         usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
    [letterArray addObject:substring];
}];

for (NSString *i in letterArray){
    NSLog(@"%@",i);
}

results in

A
B
C
D
E
F
𝍱
क्

enumerateSubstringsInRange:options:usingBlock: _{available for iOS 4+} can enumerate a string with different styles. One is called NSStringEnumerationByComposedCharacterSequences, what will enumerate letter by letter but is sensitive to surrogate pairs, base characters plus combining marks, Hangul jamo, and Indic consonant clusters, all referred as Composed Character

Note, that the accepted answer “swallows” 𝍱and breaks क् into क and ्.