NSURLConnection connecting to server, but not posting data

Question

Whenever I attempt to post something to my PHP Server, I receive the following message. It seems as if the code is connecting to the server, but no data is returned, and the pos

Answer 1

"name=%@&email=%@&phash=%@" is not a proper url-encoded string. Each key-value pair has to be separated by an '&' character, and each key from its value by an '=' character. Keys and values are both escaped by replacing spaces with the '+' character and then encoded by stringByAddingPercentEscapesUsingEncoding.

See application/x-www-form-urlencoded.

You can find a recipe how to do this in this blog post.

Answer 2

As @elk said, you should replace spaces with +. But you should percent-encode reserved characters (as defined in RFC2396).

Unfortunately, the standard stringByAddingPercentEscapesUsingEncoding does not percent escape all of the reserved characters. For example, if the name was "Bill & Melinda Gates" or "Bill + Melinda Gates", stringByAddingPercentEscapesUsingEncoding would not percent escape the & or the + (and thus the + would have been interpreted as a space, and the & would have been interpreted as delimiting the next POST parameter).

Instead, use CFURLCreateStringByAddingPercentEscapes, supplying the necessary reserved characters in the legalURLCharactersToBeEscaped parameter and then replace the spaces with +. For example, you might define a NSString category:

@implementation NSString (PercentEscape)

- (NSString *)stringForPostParameterValue:(NSStringEncoding)encoding
{
    NSString *string = CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                                                 (CFStringRef)self,
                                                                                 (CFStringRef)@" ",
                                                                                 (CFStringRef)@";/?:@&=+$,",
                                                                                 CFStringConvertNSStringEncodingToEncoding(encoding)));
    return [string stringByReplacingOccurrencesOfString:@" " withString:@"+"];
}

@end

Note, I was primarily concerned with the & and +, characters, but RFC2396 (which supersedes RFC1738) listed those additional characters as being reserved, so it's probably prudent to include all of those reserved characters in the legalURLCharactersToBeEscaped.

Pulling this together, I might have code that posts the request as:

NSDictionary *params = @{@"name" : _nameField.text ?: @"",
                         @"email": _emailField.text ?: @"",
                         @"phash": [NSString stringWithFormat:@"%d",phashnum]};

NSURL *url = [NSURL URLWithString:kBaseURLString];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

[request setValue:@"application/x-www-form-urlencoded; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:[self httpBodyForParamsDictionary:params]];

[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    if (error)
        NSLog(@"sendAsynchronousRequest error = %@", error);

    if (data) {
        // do whatever you want with the data
    }
}];

Using a utility method:

- (NSData *)httpBodyForParamsDictionary:(NSDictionary *)paramDictionary
{
    NSMutableArray *paramArray = [NSMutableArray array];
    [paramDictionary enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *obj, BOOL *stop) {
        NSString *param = [NSString stringWithFormat:@"%@=%@", key, [obj stringForPostParameterValue:NSUTF8StringEncoding]];
        [paramArray addObject:param];
    }];

    NSString *string = [paramArray componentsJoinedByString:@"&"];

    return [string dataUsingEncoding:NSUTF8StringEncoding];
}