Print symbols that were met in the text, no duplicates - ios

Question

I have been struggling with this question for couple days now. Really need your help and opinion.
We have a string, that holds a text:
NSString *contentOfFile = [[NSString alloc] initWithString:#"This is string#1"];
Now I have to log symbols, that were met in this string without duplicates. Result should look like this:
whitespace symbol here
#
1
g
h
i
n
r
s
t
I know that this is solved very simple in C code using char set and iterators but I am looking for the same simple and elegant way of handling this operation in objective-c.
I was thinking of using NSCharacterSet on the string somehow but I have a lack of knowledge in objective-c so I need your help guys please. Thanks in advance to everyone who replies.

Answer 1

Take advantage of a trait of NSSet: Its members are distinct.
NSString *contentOfFile = #"This is string#1";
NSMutableSet *set = [NSMutableSet set];
NSUInteger length = [contentOfFile length];
for (NSUInteger index = 0; index < length; index++)
{
NSString *substring = [contentOfFile substringWithRange:NSMakeRange(index, 1)];
[set addObject:substring];
}
NSLog(#"%#", set);
However, there's one remaining problem, and that is the members of a set are also unordered. Fortunately, arrays are ordered. So if you change the last line:
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"self" ascending:YES];
NSArray *array = [set sortedArrayUsingDescriptors:#[sortDescriptor]];
NSLog(#"%#", array);
If case insensitivity is important to you, there unfortunately is no 'case-insensitive' option for NSSet. However, you could convert your source string to all lowercase, like this:
NSString *contentOfFile = [#"This is string#1" lowercaseString];
and this would give you results exactly matching your sample output.

Answer 2

// Create the string
NSString *contentOfFile = #"This is string#1";
// Remove all whitespaces
NSString *whitespaceRemoval = [contentOfFile stringByReplacingOccurrencesOfString:#" " withString:#""];
// Initialize an array to store the characters
NSMutableArray *components = [NSMutableArray array];
// Iterate through the characters and add them to the array
for (int i = 0; i < [whitespaceRemoval length]; i++) {
NSString *character = [NSString stringWithFormat:#"%c", [whitespaceRemoval characterAtIndex:i]];
if (![components containsObject:character]) {
[components addObject:character];
}
}