NSArray of character strings

Question

I'm trying to create an NSMutableArray of characters.

lowerCaseLetters = [NSMutableArray new];
for (char crt = 'a'; crt <= 'z'; crt ++) {
    NSString *chrStr = [NSString stringWithCString:&crt encoding:NSUTF8StringEncoding];
    [lowerCaseLetters addObject:chrStr];
}
NSLog(@"%@",lowerCaseLetters);

Result:

  "a@Ip",
    "b@Ip",
    "c@Ip",
    "d@Ip",
    "e@Ip",
    "f@Ip",
    "g@Ip",
    "h@Ip",
    "i@Ip",
    "j@Ip",
    "k@Ip",
    "l@Ip",
    "m@Ip",
    "n@Ip",
    "o@Ip",
    "p@Ip",
    "q@Ip",
    "r@Ip",
    "s@Ip",
    "t@Ip",
    "u@Ip",
    "v@Ip",
    "w@Ip",
    "x@Ip",
    "y@Ip",
    "z@Ip"
)

Why do I get this? Is there a better way to do this? PS: Sometimes this crashes with "insertObject:atIndex:" can not insert nil object.... Why?

Answer 1

This is undefined behavior:

NSString *chrStr = [NSString stringWithCString:&crt encoding:NSUTF8StringEncoding];

The problem is that &crt is not a C string, because C strings must be null-terminated. You can fix it like this:

char buf[2];
buf[0] = crt;
buf[1] = '\0';
NSString *chrStr = [NSString stringWithCString:buf encoding:NSUTF8StringEncoding];

You could also use stringWithFormat: for a simpler approach, like this:

NSString *chrStr = [NSString stringWithFormat:@"%c", crt];

Answer 2

Try this...

NSString *stringWithComma = @"a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";
NSArray *lowerCaseLetters = [[NSArray new] init];

lowerCaseLetters = [stringWithComma componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@","]];
NSLog(@"Array %@",lowerCaseLetters);

This gives you an NSArray. If you need a NSMutableArray, you have to copy from the NSArray.

or simply allocate

NSMutableArray *lowerCaseLetters = [[NSMutableArray alloc] initWithObjects: @"a", @"b",...,@"z", nil]; 

The first approach is dynamic though as you could create stringWithComma dynamically with any values in it.

Answer 3

Following on from dasblinkenlight, another approach is

for (unichar crt = 'a'; crt <= 'z'; crt ++) // note crt is now unichar
{
    NSString *chrStr = [NSString stringWithCharacters: &crt length: 1];
    [lowerCaseLetters addObject:chrStr];
}

Following on from user2734323 another approach is

lowerCaseLetters = [@[ @"a", @"b", @"c",  .... , @"x", @"y", @"z" ] mutableCopy];