Encoding string arguments for URLs - objective-c

Question

I created a method to build URLs for me.
- (NSString *)urlFor:(NSString *)path arguments:(NSDictionary *)args
{
NSString *format = #"http://api.example.com/%#?version=2.0.1";
NSMutableString *url = [NSMutableString stringWithFormat:format, path];
if ([args isKindOfClass:[NSDictionary class]]) {
for (NSString *key in args) {
[url appendString:[NSString stringWithFormat:#"&%#=%#", key, [args objectForKey:key]]];
}
}
return url;
}
When I try to build something like below, the URLs aren't encoded, of course.
NSDictionary *args = [NSDictionary dictionaryWithObjectsAndKeys:
#"http://other.com", #"url",
#"ABCDEF", #"apiKey", nil];
NSLog(#"%#", [self urlFor:#"articles" arguments:args]);`
The returned value is http://api.example.com/articles?version=2.0.1&url=http://other.com&apiKey=ABCDEF when it should be http://api.example.com/articles?version=2.0.1&url=http%3A%2F%2Fother.com&apiKey=ABCDEF.
I need to encode both key and value. I searched for something and found CFURLCreateStringByAddingPercentEscapes and stringByAddingPercentEscapesUsingEncoding but none of the tests I made worked.
How can I do it?

Answer 1

IIRC, slashes should be interpreted properly when they're in the query part of a URL. Did you test to see if it still works without encoded slashses? Otherwise, do something like:
if ([args isKindOfClass:[NSDictionary class]]) {
for (NSString *key in [args allKeys]) {
NSString *value = [(NSString*)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)[args objectForKey:key], NULL, CFSTR("/?&:=#"), kCFStringEncodingUTF8) autorelease];
[url appendString:[NSString stringWithFormat:#"&%#=%#", key, value]];
[value release];
}
}
return url;
Note the value of the 4th argument to CFURLCreateStringByAddingPercentEscapes.

Answer 2

You should consider using Google Toolbox for Mac's GTMNSString+URLArguments; it's designed for exactly this purpose.

Answer 3

I'd recommend our KSFileUtilities set of classes. Your example would then be:
- (NSString *)urlFor:(NSString *)path arguments:(NSDictionary *)args
{
NSMutableDictionary *parameters = [NSMutableDictionary dictionaryWithDictionary:args];
[parameters setObject:#"2.0.1" forKey:#"version"];
NSURL *result = [NSURL ks_URLWithScheme:#"http"
host:#"api.example.com"
path:path
queryParameters:parameters;
return [result absoluteString];
}