Cocoa - Trim all leading whitespace from NSString

Question

(have searched, but not been able to find a simple solution to this one either here, or in Cocoa docs)

Q. How can I trim all leading whitespace only from an NSString? (i.e. leaving any other whitespace intact.)

Unfortunately, for my purposes, NSString's stringByTrimmingCharactersInSet method works on both leading and trailing.

Mac OS X 10.4 compatibility needed, manual GC.

score 70 · Accepted Answer · edited May 26 '12 at 16:36

70

This creates an NSString category to do what you need. With this, you can call NSString *newString = [mystring stringByTrimmingLeadingWhitespace]; to get a copy minus leading whitespace. (Code is untested, may require some minor debugging.)

@interface NSString (trimLeadingWhitespace)
-(NSString*)stringByTrimmingLeadingWhitespace;
@end

@implementation NSString (trimLeadingWhitespace)
-(NSString*)stringByTrimmingLeadingWhitespace {
    NSInteger i = 0;

    while ((i < [self length])
           && [[NSCharacterSet whitespaceCharacterSet] characterIsMember:[self characterAtIndex:i]]) {
        i++;
    }
    return [self substringFromIndex:i];
}
@end

edited May 26 '12 at 16:36

Jonathan.

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answered Jul 08 '10 at 04:16

John Franklin

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Thanks very much John, and everyone who helped. If I change the NSInteger line for 10.4 compatibility, it works just great. Cheers. – SirRatty Jul 08 '10 at 06:12
I forgot 10.4 doesn't have NSInteger. Most of my work targets mobile devices, so it's been a while since I did anything for Tiger. I'm glad it worked! – John Franklin Jul 08 '10 at 07:19
This is very helpful. One typo: "idx" should be "i" in the while loop. – nont Mar 13 '12 at 17:24
3

Instead of doing your own while loop, use `NSString rangeOfCharacterFromSet:`, `NSString stringByTrimmingCharactersInSet:`, or if you need flexibility go for an `NSScanner` object or even Reg Ex. See other answers to this question (they have less up-votes at the moment). – Abhi Beckert Oct 05 '12 at 03:38

Hejazi · Answer 2 · 2010-12-29T17:42:10.057

49

This is another solution using Regular Expressions (requires iOS 3.2):

NSRange range = [string rangeOfString:@"^\\s*" options:NSRegularExpressionSearch];
NSString *result = [string stringByReplacingCharactersInRange:range withString:@""];

And if you want to trim the trailing whitespaces only you can use @"\\s*$" instead.

edited Dec 29 '10 at 17:42

answered Dec 28 '10 at 12:58

Hejazi

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Doesn't this trim both leading AND ending characters? – SirRatty Dec 28 '10 at 23:02
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Yes, you're right. I didn't notice that you want to remove the leading whitespaces only. Anyway, I changed the answer, check it again. – Hejazi Dec 29 '10 at 17:42
This solution is a lot more concise! Thanks for this! – pedroremedios Dec 30 '13 at 20:49

score 37 · Answer 3 · answered May 08 '12 at 18:57

37

This code is taking blanks.

NSString *trimmedText = [strResult stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

NSLog(@"%@",trimmedText);

answered May 08 '12 at 18:57

aybars

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This will remove both leading and trailing whitespaces and newline characters, while the question is how to remove ONLY those at the beginning.. – alasker May 27 '14 at 23:06

score 26 · Answer 4 · answered Nov 28 '11 at 09:15

26

Here is a very efficient (uses CoreFoundation) way of doing it (Taken from kissxml):

- (NSString *)trimWhitespace {
    NSMutableString *mStr = [self mutableCopy];
    CFStringTrimWhitespace((CFMutableStringRef)mStr);

    NSString *result = [mStr copy];

    [mStr release];
    return [result autorelease];
}

answered Nov 28 '11 at 09:15

Yosi Taguri

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The question is for trimming leading white space; this trims trailing too – Mike Abdullah May 29 '12 at 17:29
@YosiTaguri, HOw will I call this method ? to trim my NSString – Chatar Veer Suthar Feb 01 '14 at 22:41
If you don't mind trimming trailing space too, then this is the perfect answer. – KPM Jan 15 '16 at 16:03
thanks for and answer that isn't a waste of CPU like many easy whitebelt answers <3 – Drew O'Meara Sep 16 '16 at 19:11

score 21 · Answer 5 · edited Dec 08 '12 at 20:40

21

 NSString *myText = @"       foo    ";    
 NSString *trimmedText = [myText stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
 NSLog(@"old = [%@], trimmed = [%@]", myText, trimmedText);

edited Dec 08 '12 at 20:40

Adam

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answered Apr 20 '12 at 19:42

Ramesh

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Perfect one. Nice answer . Please follow this post. – Abdul Yasin Sep 24 '14 at 13:02

score 3 · Answer 6 · edited Dec 16 '12 at 18:29

3

Here's what I would do, and it doesn't involve categories!

NSString* outputString = inputString;
NSRange range = [inputString rangeOfCharacterFromSet: [NSCharacterSet whitespaceCharacterSet]
    options:0];
if (range.location == 0) 
    outputString = [inputString substringFromIndex: range.location + range.length];

This is much less code.

edited Dec 16 '12 at 18:29

zpasternack

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answered Jul 08 '10 at 05:27

lucius

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It's only less code if you only want to trim white space in one place in your application. – JeremyP Jul 08 '10 at 10:26
It would be faster too if you passed in the NSAnchoredSearch option – Mike Abdullah May 29 '12 at 17:30
@JeremyP you could always put it this code in a category. It is still less code. – Abhi Beckert Oct 05 '12 at 03:33
1

`rangeOfCharacterFromSet:` returns the range of the *first* character in the string. This is only going to remove the first whitespace character, not all leading. – zpasternack Dec 16 '12 at 18:36

score 0 · Answer 7 · answered Jul 08 '10 at 04:17

I didn't really have much time to test this, and I'm not sure if 10.4 contains the UTF8String method for NSString, but here's how I'd do it:

NSString+Trimming.h

#import <Foundation/Foundation.h>

@interface NSString (Trimming)

-(NSString *) stringByTrimmingWhitespaceFromFront;

@end

NSString+Trimming.m

#import "NSString+Trimming.h"

@implementation NSString (Trimming)

-(NSString *) stringByTrimmingWhitespaceFromFront
{
    const char *cStringValue = [self UTF8String];

    int i;
    for (i = 0; cStringValue[i] != '\0' && isspace(cStringValue[i]); i++);

    return [self substringFromIndex:i];
}

@end

It may not be the most efficient way of doing this but it should work.

Where is the string that is getting trimmed in the above code? Do we definitely need to write a method for this? — Pradeep Reddy Kypa, Mar 14 '12 at 11:28

score -6 · Answer 8 · answered Nov 20 '12 at 07:49

-6

str = [str stringByReplacingOccurrencesOfString:@" " withString:@""];

answered Nov 20 '12 at 07:49

NSCry

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@" This string "; becomes @"Thisstring"; . The originator stated that all other whitespace needed to remain intact. – bneely Nov 22 '12 at 00:12
Please read the question before you post an answer. The question is about trimming a string on both sides. – codetiger Jul 11 '13 at 05:04

Cocoa - Trim all leading whitespace from NSString

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