Cocoa - Trim all leading whitespace from NSString - cocoa

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.

Answer 1

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

Answer 2

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.

Answer 3

This code is taking blanks.
NSString *trimmedText = [strResult stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSLog(#"%#",trimmedText);

Answer 4

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];
}

Answer 5

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

Answer 6

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.

Answer 7

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.

Answer 8

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