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

You can also use a simple while argument. There is no RegEx magic in there, so maybe it is easier to understand and alter in the future:

while([yourNSStringObject replaceOccurrencesOfString:@"  "
                         withString:@" "
                         options:0
                         range:NSMakeRange(0, [yourNSStringObject length])] > 0);

Answer 2

Another option for regex is RegexKitLite, which is very easy to embed in an iPhone project:

[theString stringByReplacingOccurencesOfRegex:@" +" withString:@" "];

Answer 3

OS X 10.7+ and iOS 3.2+

Use the native regexp solution provided by hfossli.

Otherwise

Either use your favorite regexp library or use the following Cocoa-native solution:

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

NSCharacterSet *whitespaces = [NSCharacterSet whitespaceCharacterSet];
NSPredicate *noEmptyStrings = [NSPredicate predicateWithFormat:@"SELF != ''"];

NSArray *parts = [theString componentsSeparatedByCharactersInSet:whitespaces];
NSArray *filteredArray = [parts filteredArrayUsingPredicate:noEmptyStrings];
theString = [filteredArray componentsJoinedByString:@" "];

Answer 4

Regex and NSCharacterSet is here to help you. This solution trims leading and trailing whitespace as well as multiple whitespaces.

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

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

NSString *final = [squashed stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

Logging final gives

"Hello this is a long string!"

Possible alternative regex patterns:

• Replace only space: [ ]+
• Replace space and tabs: [ \\t]+
• Replace space, tabs and newlines: \\s+

Performance rundown

• This solution: 7.6 seconds
• Splitting, filtering, joining (Georg Schölly): 13.7 seconds

Ease of extension, performance, number lines of code and the number of objects created makes this solution appropriate.

Answer 5

Alternative solution: get yourself a copy of OgreKit (the Cocoa regular expressions library).

• OgreKit (Japanese webpage -- code is in English)
• OgreKit (Google autotranslation):

The whole function is then:

NSString *theStringTrimmed =
   [theString stringByTrimmingCharactersInSet:
        [NSCharacterSet whitespaceAndNewlineCharacterSet]];
OGRegularExpression  *regex =
    [OGRegularExpression regularExpressionWithString:@"\s+"];
return [regex replaceAllMatchesInString:theStringTrimmed withString:@" "]);

Short and sweet.

If you're after the fastest solution, a carefully constructed series of instructions using NSScanner would probably work best but that'd only be necessary if you plan to process huge (many megabytes) blocks of text.

Answer 6

Actually, there's a very simple solution to that:

NSString *string = @" spaces in front and at the end ";
NSString *trimmedString = [string stringByTrimmingCharactersInSet:
                                  [NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSLog(@"%@", trimmedString)

(Source)