Efficient way for multiple stringByReplacingOccurrencesOfString

Question

Can I do this with less code?

urlString = [urlString stringByReplacingOccurrencesOfString:@" " withString:@""];
urlString = [urlString stringByReplacingOccurrencesOfString:@"\t" withString:@""];
urlString = [urlString stringByReplacingOccurrencesOfString:@"\n" withString:@""];
urlString = [urlString stringByReplacingOccurrencesOfString:@"\r" withString:@""];

If a string contains these *in the middle of it*, do you want these to be removed, or just those at the beginning and end? — JRG-Developer, Dec 19 '13 at 00:11
Use an array in a while loop with a dynamically increasing variable which is then also used in `objectAtIndex:(intVar)` — Albert Renshaw, Dec 19 '13 at 00:15

JRG-Developer · Accepted Answer · 2013-12-19T00:12:56.740

4

If you're just wanting to trim the white space and blank lines from the beginning and end of the string, you can use

urlString = [urlString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

This includes all of the examples you've given.

edited Dec 19 '13 at 00:12

answered Dec 19 '13 at 00:05

JRG-Developer

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Never knew about that "trimming" method!! Sweet! :) – Albert Renshaw Dec 19 '13 at 00:14

score 0 · Answer 2 · answered Dec 19 '13 at 00:12

You could use a regex to remove whitespace from a string, with whitespace being anywhere in the string.

NSString *removeWhitespaceRegex = @"\\s";   

NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:removeWhitespaceRegex
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];

NSString *string = @"Remove whitespace from this string.";

NSString *modifiedString = [regex stringByReplacingMatchesInString:string
                                                           options:0
                                                             range:NSMakeRange(0, [string length])
                                                      withTemplate:@""];

NSLog(@"%@", modifiedString);

Just a disclaimer, the code above is written by heart with a quick lookup of some methods, some things might not work, but the idea behind it should.

The second, probably quicker way is to use an NSCharacterSet such as the JRG-Developer has mentioned, but this will remove only trailing whitespace.

Yes, `stringByTrimmingCharactersInSet` will only remove trailing or beginning characters in the set. I've updated my answer to reflect this. — JRG-Developer, Dec 19 '13 at 00:14
If you really were looking for *some pattern* of characters, regex would be the way to go. However, in this instance where it appears the OP is looking for spaces, newlines, etc, I'd expect that regex would wind up hindering performance compared to simply doing `stringByReplacingOccurrencesOfString:` as OP shows... — JRG-Developer, Dec 19 '13 at 00:24

Efficient way for multiple stringByReplacingOccurrencesOfString

2 Answers2