NSString extension

NSString+StringExtension.h

// NSString+StringExtension.h
//
#import <Foundation/Foundation.h>

@interface NSString (StringExtension)

// Trim off leading and trailing whitespaces
//
-(NSString*) trim;

// Trim off trailing whitespaces
//
-(NSString*) trimEnd;

// Trim off leading whitespaces
//
-(NSString*) trimStart;

// Return YES if string is ""
//
-(BOOL)isEmpty;

// Return a substring
//
-(NSString *)substringFrom:(NSUInteger)from to:(NSUInteger)to;

@end

NSString+StringExtension.m

// NSString+StringExtension.m
//
#import "NSString+StringExtension.h"


@implementation NSString (StringExtension)

- (NSString*)trim
{
    return [self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

- (NSString*)trimEnd
{
    return [self stringByTrimmingTrailingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}

- (NSString*)trimStart
{
    return [self stringByTrimmingLeadingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}


- (BOOL)isEmpty
{
	return [self isEqualToString:@""];
}

- (NSString*)substringFrom:(NSUInteger)from to:(NSUInteger)to
{
	NSString *rightPart = [self substringFromIndex:from];
	return [rightPart substringToIndex:to - from];
}


- (NSString *)stringByTrimmingLeadingCharactersInSet:(NSCharacterSet *)characterSet
{
    NSUInteger location = 0;
    NSUInteger length = [self length];
    unichar charBuffer[length];
    [self getCharacters:charBuffer];

    for (; location < length; location++)
    {
        if (![characterSet characterIsMember:charBuffer[location]])
            break;
    }

    return [self substringWithRange:NSMakeRange(location, length - location)];
}

- (NSString *)stringByTrimmingTrailingCharactersInSet:(NSCharacterSet *)characterSet
{
    NSUInteger location = 0;
    NSUInteger length = [self length];
    unichar charBuffer[length];
    [self getCharacters:charBuffer];

    for (; length > 0; length--)
    {
        if (![characterSet characterIsMember:charBuffer[length - 1]])
            break;
    }

    return [self substringWithRange:NSMakeRange(location, length - location)];
}

@end