#import <Foundation/Foundation.h>

@interface NSString(Utilities)

-(BOOL) isURL;

@end

#import "NSStringUtilities.h"

@implementation NSString(Utilities)

-(BOOL) isURL

{

    if ([self hasPrefix:@"http://"]) {

        return YES;

    }else{

        return NO;

    }

}

@end

#import <Foundation/Foundation.h>

#import "NSStringUtilities.h"

int main(void)

{

    @autoreleasepool {

        NSString* string1=@"http://www.google.com";

        NSString* string2=@"Pixar";

        if ([string1 isURL]) {

            NSLog(@"string is a url");

        }

        if ([string2 isURL]) {

            NSLog(@"string2 is a url");

        }

    }

}