Objective-C: Find consonants in string - iphone

Question

I have a string that contains words with consonants and vowels. How can I extract only consonants from the string?
NSString *str = #"consonants.";
Result must be:
cnsnnts

Answer 1

You could make a character set with all the vowels (#"aeiouy")
+ (id)characterSetWithCharactersInString:(NSString *)aString
then use the
- (NSString *)stringByTrimmingCharactersInSet:(NSCharacterSet *)set
method.
EDIT: This will only remove vowels at the beginning and end of the string as pointed out in the other post, what you could do instead is use
- (NSArray *)componentsSeparatedByCharactersInSet:(NSCharacterSet *)separator
then stick the components back together. You may also need to include capitalized versions of the vowels in the set, and if you want to also deal with accents (à á è è ê ì etc...) you'll probably have to include that also.

Answer 2

Unfortunately stringByTrimmingCharactersInSet wont work as it only trim leading and ending characters, but you could try using a regular expression and substitution like this:
[[NSRegularExpression
regularExpressionWithPattern:#"[^bcdefghjklmnpqrstvwx]"
options:NSRegularExpressionCaseInsensitive
error:NULL]
stringByReplacingMatchesInString:str
options:0
range:NSMakeRange(0, [str length])
withTemplate:#""]
You probably want to tune the regex and options for your needs.

Answer 3

Possible, for sure not-optimal, solution. I'm printing intermediate results for your learning. Take care of memory allocation (I didn't care). Hopefully someone will send you a better solution, but you can copy and paste this for the moment.
NSString *test = #"Try to get all consonants";
NSMutableString *found = [[NSMutableString alloc] init];
NSInteger loc = 0;
NSCharacterSet *consonants = [NSCharacterSet characterSetWithCharactersInString:#"bcdfghjklmnpqrstvwxyz"];
while(loc!=NSNotFound && loc<[test length]) {
NSRange r = [[test lowercaseString] rangeOfCharacterFromSet:consonants options:0 range:NSMakeRange(loc, [test length]-loc)];
if(r.location!=NSNotFound) {
NSString *temp = [test substringWithRange:r];
NSLog(#"Range: %# Temp: %#",NSStringFromRange(r), temp);
[found appendString:temp];
loc=r.location+r.length;
} else {
loc=NSNotFound;
}
}
NSLog(#"Found: %#",found);

Answer 4

Here is a NSString category that does the job:
- (NSString *)consonants
{
NSString *result = [NSString stringWithString:self];
NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:#"aeiou"];
while(1)
{
NSRange range = [result rangeOfCharacterFromSet:characterSet options:NSCaseInsensitiveSearch];
if(range.location == NSNotFound)
break;
result = [result stringByReplacingCharactersInRange:range withString:#""];
}
return result;
}