iOS下URL编码

- (NSString *)encodeToPercentEscapeString: (NSString *) input  
{  
    // Encode all the reserved characters, per RFC 3986  
    // (<http://www.ietf.org/rfc/rfc3986.txt>)  
    NSString *outputStr = (NSString *)   
    CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,  
                                            (CFStringRef)input,  
                                            NULL,  
                                            (CFStringRef)@"!*‘();:@&=+$,/?%#[]",  
                                            kCFStringEncodingUTF8);  
    return outputStr;  
}  
  
- (NSString *)decodeFromPercentEscapeString: (NSString *) input  
{  
    NSMutableString *outputStr = [NSMutableString stringWithString:input];  
    [outputStr replaceOccurrencesOfString:@"+"  
                               withString:@" "  
                                  options:NSLiteralSearch  
                                    range:NSMakeRange(0, [outputStr length])];  
  
    return [outputStr stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];  
}  

NSString * testUrl      = @"http://search.google.com?keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?%#[]";  
NSLog(@"original: %@", testUrl);  
  
NSString * encodeStr    = [self encodeToPercentEscapeString:testUrl];  
NSLog(@"encoded: %@", encodeStr);  
  
NSString * encodeStr2   = [testUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];  
NSLog(@"encoded2:%@", encodeStr2);  
  
NSString * decodeStr    = [self decodeFromPercentEscapeString:encodeStr];  
NSLog(@"decoded: %@", decodeStr);  

>> original: http://search.google.com?keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?%#[]  
>> encoded:  http%3A%2F%2Fsearch.google.com%3Fkeywords%3D%28%24%23%20it%27s%20%7Ba%2A123%7D%2900%21%2A%27%28%29%3B%3A%40%26%3D%2B%24%2C%2F%3F%25%23%5B%5D  
>> encoded2: http://search.google.com?keywords=($%23%20it‘s%20%7Ba*123%7D)00!*‘();:@&=+$,/?%25%23%5B%5D  
>> decoded:  http://search.google.com?keywords=($# it‘s {a*123})00!*‘();:@&=+$,/?%#[]