twitter error 401 - What should I do with the exclamation mark?

Question

I have a problem with Oauth and twitter api ver1.1. My app will tweet a post to twitter when post something to another site. But when the post body contains exclamation mark ('!'), I get twitter 401 error that is 'Unauthorized'. I searched on google, and found that it may related to Oauth. Some people says that the '!' must be encoded to '%21'. I tried it, but when I tweet '!' to twitter, I just got '%21' but not '!' itself. How can I encode the '!' correctly?

Answer 1

you must encode your tweet with this category

#import "NSString+URLEncoding.h"
@implementation NSString (OAURLEncodingAdditions)

- (NSString *)URLEncodedString 
{
    NSString *result = (NSString *)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                                       (CFStringRef)self,
                                                                       NULL,
                                                                       CFSTR("!*'();:@&=+$,/?%#[]"),
                                                                       kCFStringEncodingUTF8);
    [result autorelease];
    return result;
}

- (NSString*)URLDecodedString
{
    NSString *result = (NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault,
                                                                                       (CFStringRef)self,
                                                                                       CFSTR(""),
                                                                                       kCFStringEncodingUTF8);
    [result autorelease];
    return result;  
}

@end