invalid conversion specifier '+'

Question

I've looked this up but the answer always seems to be specific to that problem.

I'm trying to request info from a web server using JSON and have the info come up onto a table view. The code that is giving me trouble is below:

CalendarCommunicator.m:

#import "CalendarCommunicator.h"
#import "CalendarCommDelegate.h"


@implementation CalendarCommunicator

- (void)searchGroupsAtCoordinate:(CLLocationCoordinate2D)coordinate
{
    NSString *urlAsString = [NSString stringWithFormat:@"http://medpak.costarica.com/api/content/render/false/type/json/query/+structureName:calendarEvent%20+(conhost:9fe93d82-1cd8-46b1-9dda-8b940e407d23%20fonhost:SYSTEM_HOST)%20+languageId:1", coordinate.latitude, coordinate.longitude];
    NSURL *url = [[NSURL alloc] initWithString:urlAsString];
    NSLog(@"%@", urlAsString);

    [NSURLConnection sendAsynchronousRequest:[[NSURLRequest alloc] initWithURL:url] queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

        if (error) {
            [self.delegate fetchingGroupsFailedwithError:error];
        } else {
            [self.delegate recievedGroupsJSON:data];
        }
    }];
}

@end

In the NSString *urlAsString section I get a warning with the URL. It says '"Invalid Conversion Specifier '+'". What exactly does this mean? Are there to many '+' signs in the URL or am I missing something?

Answer 1

The reason is that % has meaning both to percent-encoding of URLs and also to format strings. In this case +stringWithFormat sees the %20+ in your string, and thinks you're giving it a format command. For literal % in your URL format string, make them %%, that is, pass %% to string formatting methods / functions to get a literal %.

However, in your particular case, I'm not sure which ones you're trying to substitute for the locations and which ones you're meaning to stand as percent-escapes.