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?

A "character string" is supposed to be null-terminated. Yours isn't, so stringWithCString blindly reads ahead until it encounters a random zero byte. — Hot Licks
– Hot Licks, Commented Jan 1, 2014 at 14:18
The single quotes are used to create character constants, double quotes are used to create strings that are nu terminated. — zaph
– zaph, Commented Jan 1, 2014 at 14:20
Keep in mind that "a-z" as lowercase letters is only valid for some languages. Other languages have either additional or completely different lowercase letters. Keep that in mind when you consider that your app may be used by people from all over the world. — rmaddy
– rmaddy, Commented Jan 1, 2014 at 20:26

Sergey Kalinichenko · Accepted Answer · 2014-01-01 14:18:21Z

2

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];

answered Jan 1, 2014 at 14:18

Sergey Kalinichenko

729k85 gold badges1.2k silver badges1.6k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

zaph Over a year ago

The last approach looks really nice!

JeremyP · Accepted Answer · 2014-01-01 14:42:20Z

1

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];

answered Jan 1, 2014 at 14:42

JeremyP

87.4k15 gold badges129 silver badges164 bronze badges

Comments

user2734323 · Accepted Answer · 2014-01-01 14:50:33Z

1

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.

edited Jan 1, 2014 at 14:50

answered Jan 1, 2014 at 14:34

user2734323

7061 gold badge8 silver badges19 bronze badges

Collectives™ on Stack Overflow

NSArray of character strings

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related