Collapse sequences of white space into a single ch

Question

Consider the following example:

"    Hello      this  is a   long       string!   "

I want to convert that to:

"Hello this is a long string!"

Answer 1

With a regex, but without the need for any external framework:

NSString *theString = @"    Hello      this  is a   long       string!   ";

theString = [theString stringByReplacingOccurrencesOfString:@" +" withString:@" "
                       options:NSRegularExpressionSearch
                       range:NSMakeRange(0, theString.length)];

Answer 2

according from @Mathieu Godart is best answer, but some line is missing , all answers just reduce space between words , but when if have tabs or have tab in place space , like this: " this is text \t , and\tTab between , so on " in three line code we will : the string we want reduce white spaces

NSString * str_aLine = @"    this is text \t , and\tTab between      , so on    ";
// replace tabs to space
str_aLine = [str_aLine stringByReplacingOccurrencesOfString:@"\t" withString:@" "];
// reduce spaces to one space
str_aLine = [str_aLine stringByReplacingOccurrencesOfString:@" +" withString:@" "
                                                    options:NSRegularExpressionSearch
                                                      range:NSMakeRange(0, str_aLine.length)];
// trim begin and end from white spaces
str_aLine = [str_aLine stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

the result is

"this is text , and Tab between , so on"

without replacing tab the resul will be:

"this is text    , and  Tab between , so on"

Answer 3

Following two regular expressions would work depending on the requirements

1. @" +" for matching white spaces and tabs
2. @"\\s{2,}" for matching white spaces, tabs and line breaks

Then apply nsstring's instance method stringByReplacingOccurrencesOfString:withString:options:range: to replace them with a single white space.

e.g.

[string stringByReplacingOccurrencesOfString:regex withString:@" " options:NSRegularExpressionSearch range:NSMakeRange(0, [string length])];

Note: I did not use 'RegexKitLite' library for the above functionality for iOS 5.x and above.

Answer 4

A one line solution:

NSString *whitespaceString = @" String with whitespaces ";

NSString *trimmedString = [whitespaceString
        stringByReplacingOccurrencesOfString:@" " withString:@""];

Answer 5

This should do it...

NSString *s = @"this is    a  string    with lots  of     white space";
NSArray *comps = [s componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

NSMutableArray *words = [NSMutableArray array];
for(NSString *comp in comps) {
  if([comp length] > 1)) {
    [words addObject:comp];
  }
}

NSString *result = [words componentsJoinedByString:@" "];

Answer 6

Here's a snippet from an NSString extension, where "self" is the NSString instance. It can be used to collapse contiguous whitespace into a single space by passing in [NSCharacterSet whitespaceAndNewlineCharacterSet] and ' ' to the two arguments.

- (NSString *) stringCollapsingCharacterSet: (NSCharacterSet *) characterSet toCharacter: (unichar) ch {
int fullLength = [self length];
int length = 0;
unichar *newString = malloc(sizeof(unichar) * (fullLength + 1));

BOOL isInCharset = NO;
for (int i = 0; i < fullLength; i++) {
    unichar thisChar = [self characterAtIndex: i];

    if ([characterSet characterIsMember: thisChar]) {
        isInCharset = YES;
    }
    else {
        if (isInCharset) {
            newString[length++] = ch;
        }

        newString[length++] = thisChar;
        isInCharset = NO;
    }
}

newString[length] = '\0';

NSString *result = [NSString stringWithCharacters: newString length: length];

free(newString);

return result;
}